Smoke is seen during a gunmen attack at the parliament's building in central Tehran.

TEHRAN: Attackers raided Iran's parliament and set off a suicide bomb at the Mausoleum of Ayatollah Khomeini in Tehran on Wednesday, killing at least 12 people in a twin assault at the heart of the Islamic Republic, Iranian media reported.

The Iranian intelligence ministry said security forces had arrested a "terrorist team" planning a third attack, without giving further details.

Islamic State claimed responsibility for the attacks in a statement.

It marks the first attack in Iran claimed by the ISIS , which is at war with Iranian-backed forces in Syria and Iraq. In a message posted through its Aamaq News Agency, the IS group claimed its fighters were behind the assaults.

The attacks began mid morning when assailants armed with Kalashnikov rifles stormed the parliament building. One of the attackers later blew himself up inside, where a session had been in progress, according to a statement carried by Iran's state TV.

Deputy interior minister Mohammad Hossein Zolfaghari told Iran's state TV the apparently male attackers wore women's attire.

The attacks, targeting parliament and the shrine of the Republic's revered founder, Ayatollah Khomeini, took place less than a month after the re-election of President Hassan Rouhani , a moderate.

Three assailants, one with a pistol and two with AK-47 assault rifles, attacked the parliament building in central Tehran, lawmaker Elias Hazrati told state television.

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Iran's state broadcaster IRIB reported that one attacker detonated a suicide vest there, though some other news agencies said the explosion might have been caused by grenades thrown by the assailants.

"I was passing by one of the streets. I thought that children were playing with fireworks, but I realized people are hiding and lying down on the streets," Ebrahim Ghanimi, who was around the parliament building when the assailants stormed in, said. "With the help of a taxi driver, I reached a nearby alley."

Police helicopters circled over the parliament building and all mobile phone lines from inside were disconnected.

Speaker Ali Larijani dismissed the attacks, saying they were a "trivial matter" and that security forces were dealing with them.

About half an hour later, attackers opened fire at the mausoleum a few kilometres south of the city, wounding several members of the public, Iran's English-language Press TV said.

One attacker detonated a suicide vest, one was killed by security forces and other assailants were arrested, the Governor of Tehran was quoted as saying by IRIB.

In addition to being lethal, the attack on the shrine of Khomeini is symbolically stunning. As Iran's first Supreme Leader, Khomeini is a towering figure in the country and was its revolutionary leader in the 1979 ouster of the shah.

"The atmosphere is tense. It is a blow to Rouhani. How can four armed men enter the parliament, where a very tight security has always been in place," said a senior official, who asked not to be named.

Rouhani retained power with a landslide victory over candidates supported by the hardline clergy and the Revolutionary Guards Corps (IRGC), the country's most powerful security force in charge of ensuring national security.

Iranian TV said parliament had resumed, and broadcast footage of what it said was the opening session proceeding normally.

Special meeting of Iran's security council

Interior minister Abdolrahman Fazli told ISNA he had convened a special meeting of the country's security council.

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.

Iran, the predominant Shia power, has been helping both Iraq and President Bashar al-Assad 's regime in Syria to battle IS.

The jihadist group is under increasing pressure in both countries, having lost significant territory in the face of offensives now targeting its last two major urban bastions, Raqa in Syria and Mosul in Iraq.

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."

IS and other extremists consider Shia to be apostates, and the video accuses Iranians of persecuting Sunnis over the centuries and into modern times.

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.



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