Human rights organizations have called for a full investigation into the deadly attacks by Nigerian forces against Shia Muslims in the northern city of Zaria late last year.

Amnesty senior research adviser Lucy Freeman described the Nigerian army’s human rights violations as “shocking,” saying soldiers “going above and beyond and outside of the rule of the law” was not unusual.

Human Rights Watch believes “at least 300” people were killed in the Nigerian forces’ attacks in December 2015, while Amnesty International puts the figure at “hundreds,” AFP reported.

The remarks came as Nigeria’s military high command has frequently been accused of abuses against civilians in the operations against Boko Haram Takfiri militants.

The military high command, however, has rejected the claims as “unsubstantiated.”

Freeman further described the killing of Shias as “part of a pattern of problems of excessive force and human rights violations by the Nigerian military.”

Moreover, HRW's senior Nigeria researcher Mausi Segun slammed the troops’ response as disturbing, adding, “There is no overt action on the part of the government to quickly respond to this situation and assure Nigerians that [President] Muhammadu Buhari is indeed the democratic leader that he claims to be, that this is not a military dictatorship.”

On December 12 last year, Nigerian soldiers attacked Shia Muslims attending a ceremony at a religious center in the northern city of Zaria, accusing them of blocking the convoy of the army’s chief of staff and attempting to assassinate him. The Shias have categorically denied the allegations.

The following day, Nigerian forces also raided Zakzaky’s home and arrested him after reportedly killing those attempting to protect him, including one of the Islamic Movement of Nigeria (IMN)’s senior leaders and its spokesman.

Both incidents led to the deaths of hundreds of members of the religious community, including three of Zakzaky’s sons. The Britain-based Islamic Human Rights Commission (IHRC) has put the death toll at over 1,000.

The Shia cleric is said to have been charged with “criminal conspiracy and inciting public disturbances.”

The IMN has called for Zakzaky’s unconditional release and for Abuja to respond to the “unjustifiable atrocities committed by the army.”

On Thursday, IMN said more than 700 of its members are still unaccounted for a month after the deadly attacks in the northern city of Zaria.