Armed assailants, including some disguised as women, stunned Iran on Wednesday with brazen attacks on the Parliament building and the tomb of its revolutionary founder, the worst terrorist strike to hit the Islamic republic in years.

At least 12 people were killed and 46 were wounded in the near-simultaneous assaults, which lasted for hours, clearly took Iran’s elite security forces by surprise and shattered the self-proclaimed image of calm in a turbulent region.

The six known attackers also were killed, official news media said, and five suspects were reported detained. Their identities were not made clear.

“We will avenge the blood of those martyred in today’s terrorism attacks,” said Brig. Gen. Hossein Salami, deputy commander of the Islamic Revolutionary Guards Corps, the country’s powerful paramilitary force.