The Islamic State claimed responsibility for attacks at Iran's parliament building and the shrine of its revolutionary leader on Wednesday.

The terrorist group released a 24-second video through Amaq, its news agency, showing footage from inside Iran's parliament building.

At least 12 people were killed in two attacks that took place Wednesday on Iran's parliament building and the shrine of Ayatollah Khomeini in Tehran, Iran officials said.

According to state media, gunmen went on a shooting spree after storming the parliament building in the republic's capital. Another attacker detonated a suicide bomb.

Attackers were also holding hostages inside the parliament building, which is surrounded by multiple security checkpoints and is heavily fortified.

Deputy Interior Minister Mohammad Hossein Zolfaghari told state television that the male attackers wore women's clothing, and four of the attackers were killed.

A simultaneous attack targeted the shrine of Ayatollah Khomeini on the outskirts of Tehran. A suicide bomber detonated a bomb there.