Islamic Movement of Nigeria spokesman Ibrahim Musa said six people were killed on Saturday and another 21 on Monday.

Nigeria's military said it killed six people and that the Shiite protesters fired first at soldiers.

Musa said Tuesday that many members were taking part in a religious procession, which coincided with a protest calling for the release of their movement's pro-Iran leader, Ibrahim Zakzaky.

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Zakzaky has been jailed since December 2015, when the military killed hundreds in a major attack on Shiites in the northern Nigerian city of Zaria.

Nigerian Muslims are predominantly Sunnis. The Shiite Muslim minorities say they are suffer religious persecution.