Terror attacks in the UK and West are likely to increase despite Isis being driven out of the Syrian city of Raqqa, analysts have warned amid fears of an al-Qaeda resurgence.

The militants’ defeat in their de facto capital has been hailed as a major victory in the three-year battle to retake swathes of Syria and Iraq, but territorial losses are being met with intensified calls for atrocities around the world.

Experts say there is no sign of the deadly trend of rudimentary but lethal Isis-inspired attacks like those in Westminster and London Bridge slowing down.

Jean-Marc Rickli, a research fellow at the Geneva Centre for Security Policy and King's College London, said Raqqa was “not the end of the story”.

“It is quite the opposite because for Isis to remain relevant they have to hit the headlines, so it will go after easier and softer targets,” he told The Independent.

“What we’re witnessing is an increase in the number of attacks in the West.

“The destruction of Isis in Syria and Iraq will probably increase this phenomenon, not only in the West but in Asia.”

MI5 chief warns that Britain is facing an unrelenting terrorist threat

Dr Rickli said that as well as the heightened threat posed by an unknown number of foreign fighters returning to their home countries, Isis has increased its drive aimed at encouraging lone-wolf style attacks – recently extending the call to women.

“The physical elimination of one group in one location doesn’t at all mean the elimination of the entire cancer [of jihadism],” he added. “The ideology is out there and that is almost impossible to destroy.”

Raffaello Pantucci, director of International Security Studies at the Royal United Services Institute (RUSI), said Isis was working hard on new ways to lure in new recruits without the promise of a utopian “Islamic State”.

“They’ve lost territory and they’ve lost Raqqa, so there’s a less obvious ‘state’ for people who were going to come and join them,” he added.

“But they have managed to spin an ideological narrative less bound to these realities, focusing on grievances and a supposed clash of civilisations.”

Adam Deen, executive director of the Quilliam Foundation, said that Isis could use images from Raqqa and other warzones as a “powerful tool” of radicalisation, having released numerous photos and videos appearing to show children and civilians killed in air strikes.

“The concern is that we’ve fallen into a sense of false victory like we did with the death of Osama bin Laden,” he added.

“Isis’ message was either to emigrate to the ‘caliphate’ or carry out an attack. Now they don’t have the former, all of their energy will be focused on the latter, even more so out of a sense of revenge.

“We’re going to see without a doubt more attacks in the West.”

Timeline: The emergence of Isis Show all 40 1 /40 Timeline: The emergence of Isis Timeline: The emergence of Isis 2000 Abu Musab al-Zarqawi (pictured here) forms an al-Qaeda splinter group in Iraq, al-Qa’eda in Iraq. Its brutality from the beginning alienates Iraqis and many al-Qaeda leaders. Timeline: The emergence of Isis 2006 Al-Zarqawi is killed in a U.S. strike. Al-Zarqawi’s successor, Abu Ayyub al-Masri, announces the creation of the Islamic State in Iraq (ISI). Reuters Timeline: The emergence of Isis 2009 Still al-Qaeda-linked ISI claims responsibility for suicide bombings that killed 155 in Baghdad, as well as attacks in August and October killing 240, as President Obama announces troop withdrawal from Iraq in March. Getty Images Timeline: The emergence of Isis 2010 Abu Bakr al-Baghdadi becomes head of ISI, at lowest ebb of Islamist militancy in Iraq, which sees last U.S. combat brigade depart. Timeline: The emergence of Isis 2012 In Syria, protests (pictured here starting in Daree) have morphed into what president Assad labelled a “real war” with emergence of a coalition of forces opposed to Assad’s regime. Syria group Jabhat al-Nusra are among rebel groups who refuse to join, denouncing it as a “conspiracy”. Bombings targeting Shia areas, killing more than 500 people, spark fears of new sectarian conflict. Sunni Muslims stage protests across country against what they see as increasingly marginalisation by Shia-led government. AP Timeline: The emergence of Isis 2013 Al-Baghdadi renames ISI as the Islamic State in Iraq and Syria, or Isis, as the group absorbs Syrian al-Nusra, gaining a foothold in Syria. In response, al-Qaeda chief Ayman al-Zawahiri (Bin Laden’s successor) concerned about Isis’ expansion orders that Isis be dissolved and ISI operations should be confined to Iraq. This order is rejected by al-Baghdadi. AFP Timeline: The emergence of Isis 2014 - January Isis fighters capture the Iraqi cities of Fallujah and Ramadi, giving them base to launch slew of attacks further south. AP Timeline: The emergence of Isis 2014 - June Isis declares itself the Caliphate, calling itself Islamic State (IS). The group captures Mosul, Iraq’s second largest city; Tal Afar, just 93 miles from Syrian border; and the central Iraqi city of Tikrit. These advances sent shockwaves around the world. Timeline: The emergence of Isis 2014 - June Around the same time Isis releases a video calling for western Muslims to join the Caliphate and fight, prompting new evaluations of extremists groups social media understanding. Timeline: The emergence of Isis 2014 - June Isis take Baiji oil fields in Iraq - giving them access to huge amounts of possible revenue. EPA Timeline: The emergence of Isis 2014 - August James Foley is executed by the group as concerns grow for second American prisoner, fellow reporter Steven Sotloff. AP Timeline: The emergence of Isis 2014 - August Obama authorises U.S. airstrikes in Iraq, helping to stall Isis’ along with action by Kurdish forces following the deaths of hundreds of Yazidi people on Mount Sinjar. Timeline: The emergence of Isis 2014 - September Isis release video showing Steven Sotloff’s murder prompting Western speculation his executioner is same man who killed Mr Foley. EPA Timeline: The emergence of Isis 2014 - September Obama tells us that America “will hunt down terrorists who threaten our country” EPA Timeline: The emergence of Isis 2014 - September Isis release a video appearing to show David Haines, who was captured by militants in Syria in 2013, wearing an orange jumpsuit and kneeling in the desert while he reads a pre-prepared script. It later shows what appears to be the aid worker's body. Rex Timeline: The emergence of Isis 2014 - September Peshmerga fighters scrabble to hold positions in the Diyala province (a gateway to Baghdad) as Isis fighters continue to advance on Iraqi capital. AFP Timeline: The emergence of Isis 2014 - October Aid worker Alan Henning is killed. Self-imposed media blackout refuses to show images of him in final moments, instead focuses upon humanitarian care. AP Timeline: The emergence of Isis 2014 - October Isis raise their flag in Kobani, which had been strongly defended by Kurdish troops. The victory goes against hopeful western analysis Isis had overextended itself, while alienating much of the Muslim population through the murder of Henning. Victory causes fresh waves of Kurdish refugees arriving in Turkey. Timeline: The emergence of Isis 2014 - November American hostage, who embarced values of Islam, Peter Kassig and 14 Syrian soldiers are shown meeting the same fate as other captives. But intelligence agencies will be poring over the apparently significant discrepancies between this and previous films. Seramedig.org.uk Timeline: The emergence of Isis 2015 - February Isis has released a video revealing the murder by burning to death of a Jordanian pilot held by the group since the end of December 2014. Reuters Timeline: The emergence of Isis 2015 - February Isis militants have released videos which appear to show the beheading of Japanese hostages Haruna Yukawa and Kenji Goto. Timeline: The emergence of Isis 2015 - February American aid worker, Kayla Mueller was the last American hostage known to be held by Isis. She died, according to her captors, in an airstrike by the Jordanian air force on the city of Raqqa in Syria, though US authorities disputed this. AP Timeline: The emergence of Isis 2015 - February Isis militants have posted a gruesome video online in which they force 21 Egyptian Coptic Christian hostages to kneel on a beach in Libya before beheading them. Egypt vowed to avenge the beheading and launched air strikes on Isis positions. AP Timeline: The emergence of Isis 2015 - February The British Isis militant suspected of appearing in videos showing the beheading of Western hostages has been named in reports as Mohammed Emwazi from London. Rex Features Timeline: The emergence of Isis 2015 - March Isis triple suicide attack has killed more than 100 worshippers and hundreds of others were injured after the group members targeted two mosques in the Yemeni capital of Sanaa. AP Timeline: The emergence of Isis 2015 - April Iraqi forces have claimed victory over Isis in battle for Tikrit and raised the flag in the city. EPA/STR Timeline: The emergence of Isis 2015 - April Isis has claimed responsibility for a suicide bomb attack in Afghanistan that killed at least 35 people queuing to collect their wages and injured 100 more. EPA Timeline: The emergence of Isis 2015 - April Isis’ media arm released a 29-minute video purporting to show militants executing Ethiopian Christians captives. The footage bore the extremist group’s al-Furqan media logo and showed the destruction of churches and desecration of religious symbols. A masked fighter made a statement threatening Christians who did not convert to Islam or pay a special tax. Timeline: The emergence of Isis 2015 - May Abu Bakr al-Baghdadi, the leader of Isis has been "incapacitated" by a spinal injuries sustained in a US air strike in Iraq. He is being treated in a hideout by two doctors from Isis’ stronghold of Mosul who are said to be "strong ideological supporters of the group". Timeline: The emergence of Isis 2015 - May Isis has also claimed responsibility for killing 300 of Yazidi captives, including women, children and elderly people in Iraq AP Timeline: The emergence of Isis 2015 - May Isis attack on Prophet Mohamed cartoon contest in Texas was its first action on US soil. Two gunmen were shot and killed after launching the attack at the exhibition. Elton Simpson and Nadir Soofi have been named as the attackers at the Curtis Culwell Centre arena in Garland. Timeline: The emergence of Isis 2015 - May Isis’s deputy leader, Abu Alaa Afri, a former physics teacher who was thought to have taken charge of the deadly terrorist group, has been killed in a US-led coalition airstrike. Timeline: The emergence of Isis 2015 - May US special forces have killed a senior Isis leader named as Abu Sayyaf in an operation aiming to capture him and his wife in Syria. Getty Images Timeline: The emergence of Isis 2015 - May Iran-backed militias are sent to Ramadi by the Iraqi government to fight Isis militants who completed their capture of the city. Government soldiers and civilians were reportedly massacred by extremists as they took control and the army fled. Charred bodies were left littering the city streets as troops clung on to trucks speeding away from the city. Ramadi is the latest government stronghold to fall to the so-called Islamic State, despite air strikes by a US-led international coalition aiming to stop its advance in Iraq and Syria. AFP Timeline: The emergence of Isis 2015 - May Isis rounded up civilians trapped in Palmyra and forced them to watch 20 people being executed in the historic city’s ancient amphitheatre. The Unesco World Heritage site was overrun by militants, threatening the future of 2,000 year-old monuments and ruins. Thousands of Palmyra’s residents fled but many are still living within the city walls, while the UN human rights office in Geneva said it had received reports of Syrian government forces preventing people from leaving until they retreated from the city. Getty Timeline: The emergence of Isis 2015 - May A group of Isis-affiliated fighters have captured a key airport in central Libya. The militants took control of the al-Qardabiya airbase in Sirte after a local militia tasked with defending the facility withdrew from their positions. Affiliates of Isis, already control large parts of Sirte, the birthplace of former Libyan leader Muammar Gaddafi and a former stronghold of his supporters. Timeline: The emergence of Isis 2015 - June The US Air Force has destroyed an Isis stronghold after an extremist let slip their location on social media. According the Air Force Times, General Herbert "Hawk" Carlisle, commander of Air Combat Command, said that Airmen at Hulburt Field, Florida, used images shared by jihadists to track the location of their headquarters before destroying it in an airstrike. Reuters Timeline: The emergence of Isis 2015 - June Kurdish forces captured a key military base in a significant victory in Raqqa as well as town of Tell Abyad. YPG fighters, backed by US-led airstrikes and other rebels, consolidated their gains, when they seized the key town on the Syria-Turkey border. They are now just 30 miles to the north of Raqqa and have cut off a major supply route deep inside Isis-held territory. Ahmet Silk/Getty Timeline: The emergence of Isis 2015 - June Isis has released gruesome footage claiming to show the murder of more than a dozen men by drowning, decapitation and using a rocket-propelled grenade as it seeks to boost morale among its fanatical supporters. Timeline: The emergence of Isis 2015 - June Isis has begun carrying out its threat to destroy structures in the ancient Syrian city of Palmyra, blowing up at least two monuments at the Unesco-protected site as Syrian government troops made advances on the Islamist’s positions. AFP

As Isis’ “caliphate” crumbles, there is an additional risk that followers unable to travel abroad will launch attacks on home soil instead – as seen in the London Bridge attack and other recent plots.

Analysts have also warned that Isis could pivot its propaganda to inspire revenge attacks borne of nostalgia for its destroyed state.

There is an additional possibility that the group could renew attempts to launch centrally organised assaults from its remaining territory in Syria and Iraq, or emerging bases elsewhere.

With Raqqa as Isis’ de-facto capital and base of operations, it presented an easy target for surveillance operations and air strikes but key operatives will be now more difficult to track.

Insurgents affiliated with the group control pockets of territory in countries including Libya, Egypt, Afghanistan, Nigeria and the Philippines – all of which could be used as future bases for international attacks.

Isis has continued efforts to expand its global operations, with an unverified video released this week claiming to show a new group of jihadis pledging allegiance in the Democratic Republic of the Congo.

Research shows that Isis’ propaganda operations has been declining over the past year, although videos, statements and magazines are still being published in multiple languages including English, Turkish, Arabic and Russian.

“Isis’ propaganda wing has taken a hit but it will continue to put out its message,” Mr Deen warned.

“Social media companies have improved removals but it’s not just about censorship, it’s about providing a counter-narrative because people will go underground to get the information.

“The alternative is where we’re struggling.”

Isis has continued to put out propaganda from warzones as it loses territory

Mr Deen, himself a former member of Anjem Choudary’s banned al-Muhajiroun network, said Quilliam was among the organisations involved in counter-extremism programmes but warned of a “long and drawn-out battle ahead”.

He suggested that returned fighters who are disillusioned with Isis and can expose the group’s hypocrisy and brutality could be used to dissuade future followers.

Experts are divided on the danger posed by returnees, who have not yet emerged in the UK in numbers once feared.

​Amarnath Amarasingam, a senior research fellow at the Institute for Strategic Dialogue, said his research indicated that jihadis who want to fight abroad and those who want to attack locally are “two different kinds of people”.

“One is more interested in leaving the sinful West and wants to help fight for what they perceive to be a more pure society – the ones who attack locally are mostly motivated by revenge and wanting to pay back the West for attacks in Syria,” he explained, warning that there was some overlap.

Mr Pantucci said former militants’ behaviour would be hard to predict, adding: “Very few go out to go off to a place like Syria and Iraq with the intention of training and coming back to be a terrorist.”

But some of the deadliest attacks in Europe have been carried out by trained foreign fighters, including the cell behind the Paris and Brussels attacks, and the Manchester bomber Salman Abedi is believed to have met Isis members in Libya.

Mr Deen said statistics show that the likelihood of carrying out a terror attack is dramatically increased for individuals who undergo combat training abroad, with those returning possibly feeling a heightened sense of grievance over Isis losses.

Youssef Zaghba, one of the London Bridge attackers, had been prevented from joining Isis in Syria

Andrew Parker, the director-general of MI5, previously revealed that seven plots have been foiled in the UK in as many months as the threat “operates at a scale and pace we have not seen before”.

“The threat is more diverse than I’ve ever known,” he said in a speech on Tuesday. “Plots online, complex scheming and also crude stabbings, lengthy planning, but also spontaneous attacks.”

Around 500 live operations are currently underway, targeting 3,000 of the most dangerous known jihadists, while at least 20,000 are being monitored after previously appearing on the counter-terrorism radar.

Analysts have warned that the real threat may be far larger as “clean skins” not previously known for extremist links are inspired to launch attacks.

Dr Amarasingam said the “glory days of Isis recruitment” that saw more than 800 British followers leave for Syria and Iraq in 2014 and 2015 are over, adding: “Their efforts at recruitment will of course continue, but their message will change, what they ask of recruits and supporters will change, and we just have to make sure we are listening carefully, both to local messages and their messages to supporters abroad.”

While Isis has been credited with driving a dramatic increase in global terror attacks since 2014, the international focus on the group has allowed its rival al-Qaeda to gather strength elsewhere.

The group was virtually written off after heavy losses in Iraq during the mid 2000s, and again with the killing of its leader in 2011, but is now operating both openly and through affiliates across the Middle East and Africa.

Dr Rickli said the group, which spawned Isis but has since publicly denounced it for being too extreme, had been gathering members in the Idlib region of Syria but still had international ambitions.

“In the future it is possible that we will see attacks in the West by both Isis and al-Qaeda supporters, we shouldn’t dismiss the rising threat of al-Qaeda that has been rebuilt and will now probably strike again in the West,” he added.