Three supporters of an imprisoned Shiite cleric were killed over the weekend in the Nigerian capital Abuja after clashes with the army, a military spokesman said.
According to Nigeria's military, soldiers transporting weapons and ammunition were "attacked" by members of the Islamic Movement of Nigeria (IMN) at the Zuba Bridge on Saturday afternoon.
The IMN members had established an "illegal roadblock denying motorists free passage" and when the military tried to clear the barrier they were met with "stiff opposition", James Myam said in a statement released on Sunday.
Soldiers opened fire on the IMN members after they "pelted the troops with stones" and attempted to "cart away the ammunition and missiles the troops were escorting", the statement said.
"Unfortunately, during the encounter three members of the sect were killed while two soldiers sustained various degrees of injuries," Myam said.
But the IMN disputed the claim, calling the military account "false" and "unsubstantiated". Spokesman Ibrahim Musa said the army had attacked a peaceful mourning procession.
"We categorically refute the storyline of the Nigerian army," he added.
Pro-Iranian cleric Ibrahim Zakzaky has been in government custody since bloody clashes between his supporters and the army broke out in December 2015.
Rights groups have accused Nigeria's military of killing more than 300 IMN supporters and burying them in mass graves during the 2015 confrontation, a charge the military strongly denies.
Zakzaky has been at loggerheads with Nigeria's secular authorities for years because of his call for an Iranian-style Islamic revolution. Northern Nigeria is majority Sunni Muslim.
His supporters have held a series of protests in Abuja over the past year to demand his release and have had a series of standoffs with police.