Police said nine people were killed in the clashes during which officers opened fire on members of the Islamic Movement of Nigeria (IMN) taking part in a procession in the northern city of Kano on Monday, but the minority sect said dozens died.
Security analysts have drawn some parallels between the IMN and Boko Haram, the Sunni Muslim jihadist group whose insurgency began in 2009.
The violence was the latest in a series of incidents involving the sect. A judicial inquiry in August reported that 347 IMN members were killed and buried in mass graves after clashes with the army in December 2015, and two sect members were killed in processions in Kaduna state in October.
“The United States is deeply concerned by the deaths of dozens of Nigerians during clashes between individuals participating in a Shia procession and the Nigerian Police Force in Kano State,” a statement by the U.S. diplomatic mission in Nigeria said.
“While the matter is still under investigation, we are troubled by the apparent disproportionate response by the police,” said the statement, issued by spokesman John Kirby, which also called for “calm and restraint on all sides”.
The U.S. said Nigeria’s government should conduct an investigation and “bring to account anyone responsible for violating the law”.
Last month, the government in Kaduna state, which is next to Kano state, declared IMN as an “unlawful society” on the grounds that its processions were a danger to peace, and said anyone convicted of being a member of the sect could be imprisoned for up to seven years.
Nigeria, Africa’s most populous nation of 180 million inhabitants, combines a predominantly Christian south and mainly Sunni Muslim north.
Human Rights Watch estimates that IMN, whose 1980s founders were inspired by the Islamic Revolution in Shi’ite Iran, has around 3 million members. The sect’s leader, Sheikh Ibrahim Zakzaky, has been held without charge since December following the clashes with the army in Zaria.
