Nigerian police fired bullets and tear gas to disperse Shi’ite Muslim protesters marching for their leader’s freedom in one of the capital’s most upmarket areas on Monday, and organizers said several demonstrators 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 millions 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 says Zakzaky must be freed after a court ruled his detention without charge illegal.

The crackdown has sparked fears that IMN could become radicalised, 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, said Muhammad. An IMN spokesperson, who was also at the protests, told Reuters at least four people were injured.