Kurdish authorities said that at least three people were killed – a Kurdish security official at the scene said the dead were the three attackers – and five wounded. Among the wounded were two Westerners who were in a restaurant across the street, witnesses said.

Brett McGurk, the deputy assistant secretary of state for Iraq and Iran, said in a post on Twitter that all consulate personnel had been accounted for and that there were no reports of injuries among them. He included the hashtag #VBIED, short for vehicle-born improvised explosive device.

The Islamic State, which is also pressing offensives in the cities of Ramadi and Baiji, claimed responsibility for the explosion in an Internet post.

The attack was the first direct assault on U.S. facilities in Iraq since the Islamic State took control of much of the northern and central areas of the country last summer, and only the second bombing in Irbil, the capital of the Kurdistan Regional Government, a city considered so safe that the United States moved many of its diplomats here from Baghdad when the Islamic State captured the city of Mosul and threatened Baghdad last year.