The Boko Haram gunmen who swept into the township of Gulak brought with them a new message. Rather than sowing afresh the terror they have brought to swathes of north-east Nigeria by opening fire, the jihadists insisted they were here to stay and residents would not be harmed.

For Nigerians who have died in their thousands at the hands of Boko Haram’s Islamist insurgents, such assurances were always going to be treated as hollow lies. Scores fled and today officials said the reality was that many in Gulak were killed in the weekend attack.

As Michael Kirshinga, a resident of the strategically important settlement, put it: “They assured us that they will not attack us, but people began to run for their lives. Some of us have fled for fear that, after subduing the soldiers, the insurgents will turn their gun barrels on us.”

The attack on Gulak may have ultimately conformed to Boko Haram’s grimly familiar modus operandi of spreading panic and spilling blood with murderous raids, bombings and beheadings.

In pictures: Nigeria kidnapped schoolgirls Show all 35 1 /35 In pictures: Nigeria kidnapped schoolgirls In pictures: Nigeria kidnapped schoolgirls Nigeria A total of 276 girls were abducted from the northeastern town of Chibok, in Borno state, which has a sizeable Christian community. Some 223 are still missing In pictures: Nigeria kidnapped schoolgirls Nigeria One of the kidnapped girls looks into a camera In pictures: Nigeria kidnapped schoolgirls Nigeria One of the missing girls talking to the camera In pictures: Nigeria kidnapped schoolgirls Nigeria The missing Nigerian schoolgirls, wearing the full-length hijab and praying in an undisclosed rural location. Boko Haram alleging they had converted them to Islam In pictures: Nigeria kidnapped schoolgirls Nigeria Girls wearing the full-length hijab holding a flag reading "There is no god, but Allah" and "Mohammed is Allah's prophet" In pictures: Nigeria kidnapped schoolgirls Nigeria A man claiming to be the leader of Nigerian Islamist extremist group Boko Haram Abubakar Shekau In pictures: Nigeria kidnapped schoolgirls Nigeria Abubakar Shekau speaks on the video In pictures: Nigeria kidnapped schoolgirls Nigeria Girls, wearing the full-length hijab and praying are filmed by an unidentified man (R) in an undisclosed rural location In pictures: Nigeria kidnapped schoolgirls Nigeria Soldiers lead the way as Chibok residents carry placards to protest the abduction of the missing schoolgirls in Maiduguri In pictures: Nigeria kidnapped schoolgirls Nigeria People carry signs as they attend a protest demanding the release of abducted secondary school girls in the remote village of Chibok in Lagos In pictures: Nigeria kidnapped schoolgirls UK Demonstrators hold banners as they protest about the kidnapping of girls in Nigeria, near the Nigerian High Commission in London In pictures: Nigeria kidnapped schoolgirls UK A protester demonstrates against the kidnapping of school girls in Nigeria, outside the Nigerian Embassy in London In pictures: Nigeria kidnapped schoolgirls UK Chief International Correspondent Christiane Amanpour and Prime Minister David Cameron appearing on the BBC1 current affairs programme In pictures: Nigeria kidnapped schoolgirls USA People participate in a "Bring Back Our Girls" campaign demonstration and candlelight vigil in Los Angeles In pictures: Nigeria kidnapped schoolgirls USA Girls holding heart shaped banners in a "Bring Back Our Girls" campaign demonstration and candlelight vigil in Los Angeles In pictures: Nigeria kidnapped schoolgirls South Africa South Africans protest in solidarity against the abduction of hundreds of schoolgirls in Nigeria by the Muslim extremist group Boko Haram and what protesters said was the failure of the Nigerian government and international community to rescue them, during a march to the Nigerian Consulate in Johannesburg In pictures: Nigeria kidnapped schoolgirls South Africa The kidnapping has ignited a viral social media campaign that has brought renewed attention to Boko Haram's campaign of violence, and protests around the world In pictures: Nigeria kidnapped schoolgirls South Africa Some of the hundreds of protests demonstrate outside the Nigeria Consulate to bring attention to the girls abducted in Nigeria, Johannesburg In pictures: Nigeria kidnapped schoolgirls South Africa South Africans from various civil society organisations protest in support of the Nigerian abducted Chibok school girls outside the South African parliament in Cape Town In pictures: Nigeria kidnapped schoolgirls Sri Lanka Participants chant slogans and hold placards during a protest to demand the return of hundreds of school girls abducted by the Boko Haram separatist group at the World Conference on Youth 2014, hosted by Sri Lanka in Colombo In pictures: Nigeria kidnapped schoolgirls USA Karilyn Coates (10) joins others in a candlelight vigil for the more than 300 girls abducted by Boko Haram in Nigeria, at All Souls Unitarian Church in Colorado Springs In pictures: Nigeria kidnapped schoolgirls USA Mia Kuumba, of the District of Columbia, brandishes a wooden stick during a rally in front of the Nigerian embassy in northwest Washington In pictures: Nigeria kidnapped schoolgirls Nigeria Mothers of the missing Chibok school girls abducted by Boko Haram Islamists gather to receive informations from officials. Nigeria's president said that Boko Haram's mass abduction of more than 200 schoolgirls would mark a turning point in the battle against the Islamists, as world powers joined the search to rescue the hostages In pictures: Nigeria kidnapped schoolgirls Nigeria Nana Shettima, the wife of Borno Governor, Kashim Shettima (C) weeps as she speaks with school girls from the government secondary school Chibok that were kidnapped by the Islamic extremist group Boko Haram, and later escaped in Chibok In pictures: Nigeria kidnapped schoolgirls Nigeria Leader of Chibok community in Abuja Hosea Sambido (R) raises a newspaper reporting the death of two of the abducted Chibok school girls during a rally pressing for the girls' release in Abuja, ahead of World Economic Forum In pictures: Nigeria kidnapped schoolgirls Nigeria Femi Falana, a lawyer and human rights activist (C) leads a mass-demonstration calling on the government to increase efforts to rescue the hundreds of missing kidnapped school girls of a government secondary school Chibok in Lagos In pictures: Nigeria kidnapped schoolgirls Nigeria Members of Lagos based civil society groups shout slogans calling for the release of missing Chibok school girls at the state government house in Lagos In pictures: Nigeria kidnapped schoolgirls Nigeria The Islamist group Boko Haram has claimed responsibility for abducting over 200 girls from their school in Chibok, Borno state. Nigerian police offered a reward of 50 million naira (about 310,000 US dollar) to anyone providing a lead on the whereabouts of the more than 200 school girls abducted by Islamist extremist group Boko Haram. Nigerian President Goodluck Jonathan has accepted an offer of help from the United States in tracking down and fighting the terrorists, US officials said In pictures: Nigeria kidnapped schoolgirls Nigeria Nigerians protest over the government's failure to rescue the abducted Chibok school girls in Port Harcourt In pictures: Nigeria kidnapped schoolgirls Nigeria Former Nigerian Education Minister and Vice-President of the World Bank's Africa division (3rd L) Obiageli Ezekwesilieze speaks as she leads a march of Nigeria women and mothers of the kidnapped girls of Chibok, calling for their freedom in Abuja In pictures: Nigeria kidnapped schoolgirls Bring Back Our Girls Michelle Obama tweeted a picture of her supporting the #BringBackOurGirls campaign Twitter In pictures: Nigeria kidnapped schoolgirls Bring Back Our Girls Malala joined calls for the kidnapped girls to be found Twitter/Malala Fund In pictures: Nigeria kidnapped schoolgirls Bring Back Our Girls Leona lewis supports #BringBackOurGirls campaign In pictures: Nigeria kidnapped schoolgirls Bring Back Our Girls Kelly Hoppen tweeted: 'Please make sure you do this, we must stand together and not forget them' In pictures: Nigeria kidnapped schoolgirls Bring Back Our Girls E.L. Rock Star tweeted: 'Join The Movement'

But the attempt to persuade its victims that it meant no harm and the raising of jihadist flags over the township was the latest evidence of a new – and yet more chilling – direction in Boko Haram’s five-year campaign to bring havoc to Africa’s most populous nation.

The group earlier this year succeeded in monopolising global attention – and outrage – when it kidnapped nearly 300 schoolgirls from the village of Chibok in April, 200 of whom remain missing.

But while the West has since concentrated its focus on the “caliphate” or religious fiefdom declared by the Islamic State in Iraq and Syria (Isis) in Iraq and Syria, a similar announcement by Boko Haram’s leader Abubakar Shekau – and a series of territorial gains – has passed largely unremarked outside Nigeria.

As the insurrection which began in 2009 this weekend seized yet more towns along Nigeria’s border with Cameroon and tightened its grip on large parts of its native Borno state, experts said Boko Haram was metamorphosing from a guerrilla movement once confined to the bush and mountain caves into a force capable of holding onto its gains.

When his fighters last month took the town of Gwoza in Borno, murdering inhabitants and again raising its jihadist flags, Shekau released a video in which he declared the area was “now part of the Islamic Caliphate”. He added that Gwoza now had “nothing to do with Nigeria”.

Scholars warned last week that Boko Haram, whose name translates colloquially as “Western education is sin” and which began life in 2002 as a movement to reject concepts such as evolution and big bang theory, was on the verge of ending government control across almost the entire state of Borno and establishing its cherished aim of a caliphate.

Intelligence agencies are concerned that what were once symbolic links between Isis and Boko Haram have now developed into a practical relationship with the Islamic State offering advice on strategy and tactics.

Emboldened by the success of Isis and now seemingly armed with armoured vehicles and artillery, observers said Boko Haram was beginning to operate more like a conventional army in Borno and the neighbouring north-eastern states of Adamawa and Yobe.

The Nigeria Security Network, a coalition of security experts and academics, said: “Unless swift action is taken, Nigeria could be facing a rapid takeover of a large area of its territory reminiscent of Isis’s lightning advances in Iraq.”

The nature of the threat was further underlined on Monday when a senior politician in Borno admitted that civil life in the state, home to three million people, has all but ground to a halt.

Alhaji Baba Ahmad Jidda, secretary to the Borno state government, said: “At this very moment, most parts of Borno state are being occupied by Boko Haram insurgents. Government presence and administration is minimal or non-existent across many parts of the state, with economic, commercial and social services totally subdued. Schools and clinics remain closed. Most settlements in the affected areas in the state have either been deserted or access to them is practically impossible.”

He added: “The threat to security of lives and property as a result of the criminal activities of the Boko Haram insurgents is everywhere.”

The capture of the strategic Borno town of Bama – since disputed by the Nigerian authorities – has raised concern that the state capital, Maiduguri, where Boko Haram was founded and long one of its key targets, will be next to come under sustained attack.

Soldiers in Nigeria’s beleaguered army this week fought off rebels outside the city and claimed to have secured a significant victory in a village just 25 miles from Maiduguri, where a raid killed dozens of insurgents and reportedly led to the capture of equipment including an armoured personnel carrier. But inside the city residents remain fearful that a fresh assault by Boko Haram, which has succeeded in cutting bridges around the area, is imminent.

Students at Maiduguri University, which sits on a dry river bed used by rebels to attack the city in the past, said they could not concentrate on end-of-term exams because of fear and sporadic gunfire.

Ibrahim Muhammad Idris told The Independent: “People are really scared. Prayers is the only thing we can do. We are writing the exams right now. At times if we go to class to read and we hear gunshots or any explosions we end it for the day.”

Asked about insurgents’ attempts to persuade civilians they will not be harmed, he added: “Them saying they won’t attack is just a trick, they want to use people as human shields. They are liars.”

The military successes of Boko Haram will deepen concern that Nigeria’s army, despite the bravery of individual soldiers and units, is unable to stop the rebel force despite pledges of military aid from London and Washington.

Reports are rife of desertions, refusals to fight, malfunctioning equipment and low morale. According to one report, soldiers are sent into battle with just 60 rounds of ammunition against well-equipped Islamists.

The crucial question remains of whether Boko Haram, whose members have previously enforced their idea of sharia law by beheading victims with chainsaws, has the longer-term capacity or will to administer its new gains.