ABUJA : At least 60 people were killed this weekend when the Nigerian army raided Shias and arrested its leader in the northern city of Zaria, the director of a local hospital said on Monday.

The army said the Islamic Movement was trying to assassinate the chief of army staff, Lieutenant General Tukur Buratai, when members of the sect blocked his convoy in Zaria on Saturday. They was conducting an annual ritual to usher in the month of Maulud, the birth month of the Holy Prophet Mohammed (PBUH).

On Sunday, the army raided several buildings connected to the sect and the home of its leader, Ibrahim Zakzaky. They arrested him and killed key members of the group, including Zakzaky's second-in-command and spokesman.

"As of yesterday, we had 60 corpses in our morgue," Khalid Lawal, the chief medical director of Ahmadu Bello University Teaching Hospital, told Reuters by phone.

Residents said they heard loud blasts during the raid. A Reuters reporter was barred entry to the cordoned-off area.

Iran condemned the attack on Monday and summoned Nigeria's representative there, according to its state news agency. Foreign Minister Mohammad Javad Zarif called on the Nigerian government to take "prompt and serious" action.

Spokesmen for Nigeria's presidency declined to comment and referred Reuters to the army spokesman, who did not answer multiple requests for comment.

A similar altercation between the sect and the army occurred last year during a procession. Zakzaky said that 30 followers and three of his children were killed.