In nearly simultaneous strikes Sunday, a pair of suicide bombers set off explosives during Muslim holiday celebrations inside two buildings housing offices of the main Kurdish parties in northern Iraq, killing at least 67 people and wounding more than 200.

The blasts killed senior members of the two parties, the Kurdistan Democratic Party and the Patriotic Union of Kurdistan, which are among the best-organized and most staunch U.S. allies in Iraq. Both groups supported the invasion that toppled President Saddam Hussein and put their large militias at the service of U.S. commanders.

The blasts are believed to be the first major strikes in Iraq in which the assailants strapped explosives to their bodies. Most suicide bombings in Iraq have involved explosives packed into cars or trucks.

The dead included the deputy prime minister of the Kurdish north. The KDP regional director for Erbil, the city’s mayor and his deputy, and the chief of police also were killed. The PUK dead included the top representative for Erbil.

In the attacks on Sunday, the bombs were synchronized to detonate at 10:30 a.m., when large crowds gathered at both headquarters and pressed into the small auditoriums as people wound in a large line to greet the dignitaries.