IS gunmen, suicide bombers launch twin attacks on Iran parliament, shrine of Khomeini in Tehran

Gunmen and suicide bombers have carried out apparently coordinated attacks on Iran's parliament and the shrine of Ayatollah Ruhollah Khomeini, killing at least 12 people and wounding 39.

The casualty toll is likely to rise as the attack is ongoing.

Four armed assailants stormed into the parliament building in central Tehran on Wednesday morning with one of the attackers blowing himself up amid an ongoing siege, state media reported.

Another group of attackers targeted the tomb of revolutionary founder Ruhollah Khomeini in the south of the capital, where two suicide bombers blew themselves up.

The Islamic State group has claimed responsibility for the attacks, which are the extremists' first major operation inside Iran, through its Amaq news agency.

Local media has reported that a security guard and another person were killed at the parliament complex and that a gardener was killed on the grounds of Khomeini's mausoleum with at least 39 people being injured in the rare twin attacks.

Parliament was in session as the attacks unfolded, with live footage showing members continuing with routine business even as gun battles were reported in surrounding office buildings.

Local media reported that police helicopters circled over the parliament building and that all mobile phone lines from inside were disconnected.

Entrance and exit gates at parliament were closed and lawmakers and reporters were ordered to remain in place inside the chamber.

At Khomeini's mausoleum, three or four assailants entered through the western entrance and opened fire before two of them detonated suicide vests, killing the gardener and wounding several people.

The city has been put into lockdown, with streets blocked and parts of the metro closed. Journalists were kept away from the shrine by police.

IS despises Shia-majority Iran and is at war with Tehran's proxies in Syria and 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 Shias to be apostates, and the video accuses Iranians of persecuting Sunnis over the centuries and into modern times.

Agencies contributed to this report.