AMNESTY International has demanded an investigation into allegations that the Nigerian army killed hundreds of people during a weekend raid on a mostly Shi’ite Muslim organisation.

Details of the weekend violence have been slow to emerge, with the three attacked areas of Zaria, northern Nigeria, still locked down and no-one allowed to enter or leave.

However, Islamic Movement spokesman Ibrahim Musa said that soldiers had carried away about 200 bodies from around the home of its leader Ibraheem Zakzaky and human rights activists say that hundreds, perhaps as many as 1,000 people, were killed.

“While the final death toll is unclear, there is no doubt that there has been a substantial loss of life at the hands of the military,” said Amnesty Nigeria director MK Ibrahim.

He reiterated earlier reports that two of Mr Zakzaky’s sons had been killed and another wounded.

The whereabouts of Mr Zakzaky, who was himself badly wounded, have not been disclosed by the army.

Nigerian Human Rights Commission spokesman Chidi Odinkalu called the attacks “a massacre” and said that Mr Zakzaky had suffered four bullet wounds and that one of his wives was killed in the raids, which began on Saturday and ended on Monday morning.

The army accepted that it had attacked sites in Zaria, claiming to have done so after 500 Shi’ites blocked the convoy of army commander General Tukur Buratai and tried to kill him.

A report from the military police said that some Shi’ites were crawling through tall grass towards his vehicle “with the intent to attack the vehicle with a petrol bomb” while others “suddenly resorted to firing gunshots from the direction of the mosque.”

This contradicted an earlier army communiqué saying that there had been “loss of lives as a result of the Shi’ite group members blocking roads and not allowing other passers-by to go about their lawful businesses and activities.”

Iranian President Hassan Rouhani called his Nigerian counterpart Muhammadu Buhari, asking the government to compensate families of the dead and injured victims.

Hundreds of Shi’ites protested in front of the Nigerian embassies in the Iranian and Indian capitals on Tuesday.