Foreign Ministry has condemned the killing of Muslims in Nigeria, saying it is a “worrisome and unacceptable” move.

“The repetition of the brutal killing of Muslims in a peaceful religious gathering, which was devoid of any threat and violence, is cause of concern and unacceptable,” Foreign Ministry Spokesman Bahram Qassemi said on Tuesday, Press TV reported.

He urged the Nigerian officials to exercise more vigilance against any act of violence and strife and adopt serious measures to prevent the recurrence of such crimes.

Nearly 100 people were martyred and hundreds more injured after the Nigerian armed forces opened fire on a group of followers of the Islamic Movement in Nigeria (IMN), the country's largest Shia group, in the northern city of Kano on Monday, the movement said.

The casualties were caused after soldiers fired live rounds and tear gas at mourners during a peaceful march held ahead of the upcoming Arba’een mourning rituals

The latest deadly attack on the mourning march comes despite a letter by the London-based Islamic Human Rights Commission (IHRC) that had called on the government of President Muhammadu Buhari to ensure the safety of the IMN followers during the Arba’een commemorations.

Followers of the Islamic Movement in Nigeria have been subjected to heavy-handed crackdown since last year when the army attacked a religious ceremony in their stronghold of Zaria in the north.

In December 2015, Nigerian forces raided the house of the IMN’s leader, Ayatollah Sheikh Ibarahim Zakzaky, and arrested him after killing those attempting to protect him, including one of the movement's senior leaders and its spokesman.