An attack by an outlawed pro-Iran Nigerian Shiite group on Sunday killed at least two law enforcement officers, police said, with three more found unconscious in the capital Abuja.

The capital's police force confirmed "an unprovoked attack by the proscribed Islamic Movement of Nigeria (IMN)... on some personnel of the Nigeria Police Force," said a statement by police spokeswoman Josephine Adeh.

During the attack on a police checkpoint, "two police personnel were killed, three left unconscious in the hospital, and three police patrol vehicles set ablaze," Adeh added.

Inspired by the Islamic Revolution in Iran in the late 1970s, the IMN still maintains close ties with Tehran.

It has long been at loggerheads with Nigeria's secular authorities and was banned in 2019.

Sunday's attackers carried out their assault wielding machetes, knives and improvised explosive devices, according to the police.

With several arrests made, Abuja's police commissioner, Benneth C. Igweh, condemned the "unprovoked attack", vowing to bring the perpetrators to justice.

"The situation is presently under control and normalcy restored," the police statement added.

In July 2021, after more than five years in prison, IMN leader Ibrahim Zakzaky and his wife were released by a court in Kaduna, in the north of the country.

A Shiite cleric, Zakzaky has repeatedly called for an Iranian-style Islamic revolution in Nigeria -- where the Muslim population is predominantly Sunni.