Suicide bombers and gunmen struck at the heart of Tehran on Wednesday, attacking the two most important symbols of the 1979 Iranian Revolution — the Parliament and the tomb of Ayatollah Khomeini, founder of the Islamic Republic.

The Islamic State, or IS, claimed responsibility for the daring breach that stunned Iran’s famed and feared Revolutionary Guards.

The strike left 12 people dead and at least 46 injured. For the IS, comprising Sunni extremists, Iran, which is primarily Shia, is the key enemy in the region. Iran is also involved in the anti-IS battles in neighbouring Iraq and Syria, where it is helping the regime of Bashar al-Assad take back territory held by IS militants.

In a statement, the Revolutionary Guards blamed the twin attacks on Saudi Arabia and the U.S., coming as they did soon after President Donald Trump’s visit to the Saudi Arabian capital Riyadh, where he openly reached out to Arab nations.