KANO - Nearly 350 dead bodies were buried in a mass grave in northern Nigeria after clashes between the army and supporters of a Shia cleric, a public official has told an inquiry into the unrest.

The testimony of Muhammad Namadi Musa, the director-general of the Kaduna State Interfaith Bureau, lends weight to claims that at least 300 people were killed in the violence in December last year.

The clashes came after the army said supporters of the cleric Ibrahim Zakzaky, who heads the Islamic Movement of Nigeria (IMN) group, tried to kill the chief of army staff.

Zakzaky has not been seen since his home and the IMN mosque in Zaria, Kaduna state, were destroyed, prompting calls for his release and criticism that the government is flouting due process.

Musa said on Tuesday he received a telephone call on December 13 requesting him to go to the state government headquarters in Kaduna city.

He told the hearing he was then ordered to travel to Zaria with the Kaduna state commissioner of police "to find out the number of corpses and how they would be buried".

At the Ahmadu Bello University Teaching Hospital (ABUTH) "we counted 156 corpses", while 191 others were collected from the army base in Zaria, he said.

"Most corpses were covered with black materials and they included women and children," he told the inquiry, saying the bodies were transported for burial in a convoy of trucks with military escort.

Earlier, the secretary to the Kaduna state government, Lawal Balarabe Abbas, said the mass burial was authorised by "a warrant obtained from a chief magistrates' court in Kaduna".

Nigeria's military, which has been accused of human rights abuses against civilians in the insurgency by Boko Haram militants, has said its troops acted appropriately.