
Iranian authorities have arrested five suspects after an ISIS attack which killed 12 and wounded 35 at the country's parliament and a shrine to Ayatollah Kohmeini on Wednesday.

The country's Revolutionary Guards blamed Saudi Arabia for the attack, saying: 'This terrorist attack happened only a week after the meeting between the U.S. President Donald Trump and the Saudi backward leaders who support terrorists.

'The fact that Islamic State has claimed responsibility proves that they [Saudi Arabia] were involved in the brutal attack.' Saudi Arabia's foreign minister denied the claims and, like the US, condemned the attack.

ISIS earlier said fighters armed with AK47s and pistols stormed parliament through the civilian entrance while disguising themselves as women by wearing burkas, shooting security guards before detonating a suicide bomb, killing at least five and wounding 25.

Meanwhile two more suicide bombers attacked a shrine to Ayatollah Khomeini, the founder of modern-day Iran, as another suicide device was detonated, killing at least two and injuring another 10.

The Guards' accusation dramatically escalates already-strained tensions on the Arabian Peninsula, coming after Saudi Arabia led a group of six nations in cutting ties with Qatar, saying the country supported 'Iranian terrorist groups'.

ISIS has claimed its first ever terror attack in Iran after fighters stormed parliament and attacked a shrine to Ayatollah Kohmeini (pictured, images released by the terror group claiming to show a fighter inside parliament). Four jihadi fighters got into parliament through the visitor door while disguised as women in burkas before filming part of their rampage inside, including the body of a government worker

Four terrorists stormed the parliament building in Tehran on Wednesday morning before taking hostages, as some were passed to safety from the windows

Anti-terror police exchanged fire with the attackers in a northern part of the building before a suicide bomb detonated on the fourth floor (pictured, the attackers)

Security forces stood guard as women and children were evacuated from the windows of the lower floors to rescuers below

While ministers continued sitting inside the main chamber, government workers were rushed from the building as security services engaged jihadis in a gun battle several floors above

Elsewhere two more suicide bombers targeted a shrine to Ayatollah Kohmeini, with one blowing themselves up (pictured)

Police said the shot the second suicide attacker dead before he could detonate his device (body of dead attacker pictured)

Snipers (right) were positioned around parliament while security forces made their way inside to deal with the four attackers

Security surrounded parliament as oine jihadi blew himself up inside parliament while another three were shot dead

While ISIS regularly attacks Iran's border regions, this is the first to take place inside a majority city targeting civilians

Parliament (pictured right) was placed on lockdown after attackers stormed it on Wednesday morning, with all doors and gates leading out of the building being sealed

ISIS threatened to carry out an attack inside Iran last month in a rare message issued in Persian, and today followed through on that threat (pictured, an armed member of the police)

As armed guards moved in, helicopters circled overhead and phone lines were disconnected to stop the attackers escaping

Medical workers and ambulances rushed to the scene of the attack, but were unable to save at least five people who died at parliament. At least 25 others were wounded

Police helicopters were seen flying low over parliament and the Ayatollah's shrine (pictured) following the ISIS terror attack

Riyadh also said 'authorities in Doha' have supported the Iran-backed Houthi armed group fighting against Saudi forces in Yemen.

Supreme leader Ayatollah Ali Khamenei said the deadly attacks in Tehran claimed by the Islamic State group were mere 'fire-crackers' that would have no effect on the Iranian people.

'The Iranian nation is moving forward and these fire-crackers that happened today will not have the slightest effect on the will of the people,' Khamenei told students in the capital.

Saudi Arabia is predominantly made up of Sunni Muslims, including its extensive royal family, while Iran is staunchly Shia - making them ideologically opposed.

Iran's accusation also comes the day after Donald Trump praised Saudi Arabia and took partial credit for its moves against Qatar, saying it could be 'the beginning of the end of the horror of terrorism'.

Saudi Arabia's promotion of a fundamentalist sect of Islam called Wahhabism has led to the nation being linked with ISIS in the past, as this is where the group draws much of its extremist teachings from.

Many top ISIS clerics also spent time studying or living in Saudi Arabia. The kingdom has also been accused of funding the group and turning a blind eye as citizens funneled money to it, though it has staunchly denied this.

Earlier in the day, anti-terror police in Tehran said they exchanged fire with militants in the northern part of parliament before a bomb detonated on the fourth floor.

Video purporting to be from inside the building showed a fighter armed with an AK47 moving between rooms as a dead body lay on the floor.

Government forces say all four attackers inside parliament have now been shot dead by police.

Security forces said a second attacker at the shrine had been shot dead after the first blew up, while another two people were arrested.

Tourists at the mausoleum were locked inside to keep them safe and later released.

The unusual attacks prompted the interior ministry to call for an urgent security meeting, according to the state-run IRNA news agency.

Iranian state media said police helicopters were circling over the parliament building and that all mobile phone lines from inside were disconnected.

The semi-official ISNA news agency said all entrance and exit gates at parliament were closed and that politicians and reporters had been ordered to stay inside the chamber, where a session had been in progress.

It quoted politician Elias Hazrati as saying the attackers were armed with Kalashnikov assault rifles.

It described the shrine attackers as 'terrorists' and said one carried out a suicide bombing, without providing further details.

'WORSE THAN KUFFAR': WHY ISIS HATES IRAN Jihadist groups have clashed frequently with security forces along Iran's borders with Iraq and Afghanistan, but the country has largely escaped attacks within its urban centres - until now. As the seat of Shia Muslim power in the Middle East, Iran represents everything that the Sunni terror group detests. ISIS views Shia Muslims as apostates, effectively devil-worshipers, and considers them to be below even kuffar - or non-believers. Iran has also been lending support to Iraqi forces and Syrian dictator Bashar al-Assad in fighting the terror group across its so-called caliphate. ISIS is under increasing pressure in Iraq and Syria, having lost significant territory in the face of offensives now targeting its last two major urban bastions, Raqa and Mosul. The terror group is now increasingly focusing its efforts on suicide attacks outside of the two countries. IS published a rare video in Persian in March, warning that it 'will conquer Iran and restore it to the Sunni Muslim nation as it was before.' Militant groups are also known to operate in Iran's southeastern Sistan-Baluchistan province, which borders Pakistan and has a large Sunni community. Jaish-ul Adl (Army of Justice), which Tehran accuses of links with Al-Qaeda, has carried out several armed attacks inside Iranian territory in recent years. Iran's supreme leader Ayatollah Ali Khamenei said on Sunday that attacks by IS in Europe and elsewhere showed that Western policies in the Middle East have backfired. 'This is a fire that (Western powers) themselves ignited and now has backfired on them,' he told a gathering of senior officials in Tehran. Charlie Winter, of the International Centre for the Study of Radicalisation and Political Violence at King's College, London, said the attack will lead to a deepening of sectarian tensions in the region. He said a disproportionate response inside Iran would provide ISIS with propaganda and convince those on the fence to join the terror group. Meanwhile stepped-up efforts in Iraq and Syria will be manipulated to suggest Shia Islam is waging a war on Sunnis, which is a key part of ISIS ideology. The attack itself will also help ISIS propaganda efforts and boost morale at a time when it is defending its last strongholds in Mosul and Raqqa, he said. Lastly, increased counter-terror efforts by Iran are likely to cause tensions among the Arab coalition dedicated to fighting ISIS. Advertisement

Government workers run for cover inside the main parliament chamber as ISIS militants rampaged through the building

Armed officers also made their way into the parliament chamber, where members had continued sitting during the attack

Armed guards outside parliament remained on high alert on Wednesday following ISIS's first terror attack inside Iran

Observers say security at parliament was lax before the attack, as the bombers came in through the main entrance in burkas

Guards stayed on high alert outside the building even after all four ISIS attackers were confirmed dead by security services

Police said all four parliament attackers had been killed by Wednesday afternoon, as images emerged of blood on the pavement outside

A body (bottom left) was pictured on the ground outside parliament as police and onlookers rushed to the scene of the attack

Reporters wearing bullet-proof vests, members of the public and security forces sheltered up against the gates of parliament following the early-morning attack

Men armed with AK47s and pistols shot security guards dead and wounded several others at Tehran's parliament as ambulances rushed to the scene (pictured)

Despite multiple ambulances, security forces and police on the scene, business was reported to be continuing as normal inside parliament

State TV insisted that parliament had resumed session shortly after the attack, despite images of wounded lying in the streets outside (pictured)

State news channels sought to downplay the attacks, saying that parliament had resumed session shortly after the first reports of gunfire.

Other TV channels either stopped reporting on the attacks shortly after they began, or failed to mention them altogether.

The raids come during the holy month of Ramadan and shortly after President Hassan Rouhani was reelected.

Thomas Erdbrink, bureau chief for the New York Times, reports that the attacks will come as a personal embarrassment to Rouhani, who ran on his security record.

He also reports that the shrine is largely used by foreign tourists, and that security was lax when he visited last month.

The mausoleum is in southern Tehran, around 20 kilometres (12 miles) from the parliament building.

Shia Iran has been singled out as a target by Sunni jihadists, including the Islamic State group, but has largely escaped attacks within its urban centres.

Iran provides key ground forces against IS and other rebel groups in Syria and Iraq.

The Kremlin said that an attack on two targets in Tehran by armed men underlined the need for countries to pool their efforts to fight against terrorism, something it said meant working closely with Muslim nations.

Ambulances gathered outside parliament along with members of the public as four ISIS militants attacked the building

Emergency services rushed to the parliament building (left) as gunmen were seen leaning out of the windows

Wednesday's attack on parliament (stock image) comes during the holy month of Ramadan and after President Hassan Rouhani was reelected

Tourists at Kohmeini's shrine (file image) were locked inside for their safety as police shot one attacker dead