At least 30 people were killed as in a suicide bombing at a Shiite shrine north of Baghdad, security officials said on Friday, the latest attack claimed by Islamic State militants.

Three suicide bombers dressed in military uniform opened fire on worshipers gathered at the shrine in Balad late Thursday, said Brig. Gen. Yahya Rasoul, a spokesman for the Iraqi military. Two then blew up their vests at the gate of a shrine, and a third was killed before he detonated, he said.

Dozens of people were also injured, the military said. A medical official from Balad hospital, who declined to be named because he was not authorized to give the information to the press, said 35 were killed and 65 injured.

The incident comes less than a week after Islamic State's worst suicide bombing in the country, which killed at least 292 people in Baghdad in the early hours of Sunday morning. The militants were linked to a string of other attacks during the Muslim holy month of Ramadan, including attacks in Turkey and Saudi Arabia, though they did not claim them.

On Thursday night the shrine in Balad, 60 miles north of Baghdad, was packed with pilgrims visiting to mark Eid al-Fitr, a festival held at the end of Ramadan, said Ali Bandar 27. Most of the dead were pilgrims, he said. The blast set off a fire in the area.

Islamic State militants claimed responsibility in a statement circulated online.

Shiite cleric Moqtada al-Sadr ordered his militiamen to deploy to protect the shrine. His supporters are expected to hold a protest in Baghdad on Friday, calling for government reform.