Islamic State claims to have carried out twin gun and bomb attacks on Iran's parliament and the shrine of the modern country's founder, Ayatollah Khomeini.

At least 12 people were killed and 42 injured when several gunmen and suicide bombers targeted the two locations in Tehran.

Four attackers at the parliament were killed and the fate of four reported hostages is unclear.

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One of the assailants is believed to have blown himself up on the fourth floor.


Photos showed people climbing down from exterior windows of the building as they tried to escape.

Iranian security forces were seen hiding behind bollards and running for shelter carrying guns.

Image: Iranian forces could be seen taking cover in central Tehran

A 24-second video released by Islamic State's Amaq news agency while the siege was ongoing purported to have been filmed inside the parliament building.

It showed a gunman and the bloody, lifeless body of a man lying on the ground.

Image: Ayatollah Ruhollah Khomeini pictured in 1979. He died 10 years later

A voice on the video praises God in Arabic and says: "Do you think we will leave? We will remain! God willing."

An interior ministry official said the attackers had been dressed as women and gained access through a visitors' entrance.

Image: The mausoleum of Ayatollah Ruhollah Khomeini was targeted

At the same time as the parliament siege, two militants attacked the mausoleum of the country's venerated revolutionary leader Ayatollah Khomeini, in the south of the city.

A gardener was killed and several others were injured when one exploded a suicide vest. The other attacker was shot dead.

Iran, an ally of Syria's Bashar al Assad, backs Shia militia that are waging war on IS militants in both Iraq and Syria.

Image: Members of Iranian forces take cover during an attack on the Iranian parliament

IS, a Sunni organisation, has been losing ground in both countries.

Iran's leaders sought to play down the attacks, with neither President Hassan Rouhani nor supreme leader Ayatollah Ali Khamenei commenting by early evening.

Iran's Revolutionary Guards claimed the attack was linked to the meeting between Saudi Arabian leaders - who they regard as enemies - and Donald Trump.

Image: Iranian MPs attempt to continue their session amid a terror attack on their building

A statement published by the Guards said: "This terrorist attack happened only a week after the meeting between the US president (Donald Trump) and the (Saudi) backward leaders who support terrorists.

"The fact that Islamic State has claimed responsibility proves that they were involved in the brutal attack."

Some members of parliament attempted to show they were undeterred by posting selfies of themselves in the chamber as regular business continued, despite the ladders that were brought in to help staff escape.