ABUJA (Reuters) - Nigerian police fired bullets and tear gas to disperse Shi’ite Muslim protesters marching for their leader’s freedom in the capital on Monday, and organizers said at least one demonstrator was killed and several were wounded by gunfire.

Islamic Movement of Nigeria (IMN) leader Ibrahim Zakzaky has been jailed since December 2015, when security forces killed hundreds of members in a crackdown on a group estimated to have 3 million followers.

The violent repression of the group and the detention of its leader have drawn accusations that President Muhammadu Buhari’s government is abusing human rights. The IMN, which has held regular peaceful protests in Abuja in recent months, says Zakzaky must be freed after a court ruled his detention without charge illegal.

The crackdown has sparked fears that IMN could become radicalized, in much the same way the Sunni Muslim militant group Boko Haram turned into a violent insurgency in 2009 after police killed its leader.

“As we started protesting they started shooting tear gas and using water cannons,” Abdullahi Muhammad, an IMN youth leader, told Reuters by phone. “We refused to disperse and they used bullets as well, and they shot so many people.”

“They want to push us to violence but they couldn’t, so that is why they are using live ammunition, thinking that killing will stop us. No amount of killing will stop us,” he added.

Muhammad said he witnessed police dragging bullet-hit protesters into a van and sitting on them, adding that he did not know if they were dead or alive.

At least eight other IMN members were hit by bullets and were now receiving treatment, Muhammad told Reuters. An IMN statement said at least one protester was killed.

Police said in a statement the protesters had injured 22 officers, and they arrested 115 demonstrators.

The IMN statement said about 230 members were arrested.

Nearly all of the Muslims that make up around half of Nigeria’s population are Sunnis. The IMN was founded in the 1980s after the revolution in mainly Shi’ite Iran in 1979, which inspired the group’s founders.

A judicial inquiry after the December 2015 clashes concluded that the military had killed 347 IMN members in Zakzaky’s home base, the city of Zaria. Soldiers buried the bodies in mass graves. The group calls the incident “the Zaria massacre”.

A Reuters journalist near the scene of Monday’s demonstration heard gunshots ring out and was stung by tear gas in the air.

Videos uploaded on social media showed wreaths of the gas enveloping Abuja’s streets in the upmarket Maitama district, near the landmark Transcorp Hilton hotel. Other videos showed protesters pelting an armored police vehicle with rocks before it sped away, and people fleeing the area.

“The only thing that will stop these protests is when the government frees our leader,” said Muhammad.