LAGOS, Nigeria — Nigerian troops Wednesday buried the bodies of hundreds of victims of an alleged military massacre of Shiite Muslims to hide the death toll, the Shiite Islamic Movement in Nigeria said.

Wednesday’s allegation comes as human rights advocates and the United States called for an investigation following the army’s raid on Nigerian Shiites in which hundreds of people were reportedly killed and Shiite leader Ibraheem Zakzaky suffered four bullet wounds.

The military said it acted after Shiites tried to assassinate Nigeria’s army chief.

Army spokesman Col. Sani Usman did not immediately respond to an email late Wednesday requesting comment on the burial charges.

Details of the weekend violence in Zaria have been slow to emerge because the three attacked areas of the northern town have been on lockdown with no one allowed to enter or leave.

Shiite spokesman Ibrahim Musa said soldiers took the bodies from the mortuary of Ahmadu Bello University Teaching Hospital and buried them in mass graves on Wednesday.

His statement did not explain how he got the information.

“The Nigerian army has desecrated our dead,” Musa said. “We hereby demand the location of the mass burial, and the interrogation of those who ordered the operation.”

Human rights groups say as many as 1,000 people may have been killed.