IMN leaders say group founder suffered a stroke this week in detention as protests spread to Lagos.

Police have fired guns and tear gas in a clash with a protesting group of Nigeria‘s Shia Muslims in the capital Abuja, witnesses said, just two days after a peaceful protest turned violent just outside the parliament.

Two witnesses heard gunshots and one saw policemen fire their weapons in an effort to disperse hundreds who gathered outside government buildings to demand the release of their leader Ibrahim el-Zakzaky, who has been in detention since 2015.

One witness said it did not appear the police were aiming at protesters, but they appeared to be firing live rounds.

The confrontation comes two days after clashes with police left at least two dead and 40 protesters in police custody.

Protesters ran and threw stones as police tried to disperse the crowds. A witness saw police arrest at least a dozen protesters.

The Islamic Movement of Nigeria (IMN), a group that represents Nigeria’s minority Shia Muslims, said it will continue protesting until they secure the release of el-Zakzaky, the Islamic scholar who founded the IMN in the early 1980s.

Tuesday’s protests in Abuja left two people dead and 40 in custody [Afolabi Sotunde/Reuters]

On Tuesday, Nigeria’s National Assembly went into lockdown after gunshots erupted during a violent confrontation between the sides. Each side blamed the other for the gunfire.

Senior IMN leaders told Al Jazeera they have credible information that el-Zakzaky suffered a stroke earlier this week.

“Security officers told us that the sheikh suffered another stroke on Monday,” said Abdullahi Musa, general secretary of the academic forum of IMN. “His condition is seriously deteriorating. There’s an urgent need for him to be flown abroad for medical treatment. That’s why we keep on protesting.

“We are calling on Buhari [Nigeria’s president] and his accomplices to release him.”

BREAKING NEWS: Again, Shiites Hold Massive Protest In Abuja, Say They Are Ready To Die | Sahara Reporters

"His life is in danger and there is no reason for us to go back and sit down at home. The oppressors always brutalise, oppress…"@PoliceNG READ MORE: https://t.co/n8I8fnZsfT pic.twitter.com/JHTnsuzERR — Sahara Reporters (@SaharaReporters) July 10, 2019

A presidential spokesperson said el-Zakzaky, who has been at loggerheads with Nigeria’s Sunni-led government at state and federal levels for years, was being held “for his own good”.

The comments have only served to enrage members of the IMN who have mostly been peaceful in their demands. The police said some IMN members dispossessed an officer of his weapon during Tuesday’s protests, leading to five policemen being shot and two protesters being killed.

In videos shared on social media, live ammunition was fired at protesters on Wednesday around the heavily guarded Three Arms Zone in Abuja. An unknown number of protesters were also arrested.

The new wave of protests have also spread to the commercial capital of Lagos, almost 800km south of Abuja, despite the arrest of more than 40 IMN members and the death of at least two more on Tuesday.

“The police brutality and inhumanity is only going to give us more courage to keep protesting until our leader is released,” said Musa.

Abdullahi Murtala, security analyst with the Abuja-based Goro Initiative, believes that the Shia Muslims are “emboldened by the perceived injustice of an ‘immoral state'” and will continue their protest and show of defiance against the Buhari government.

“Indiscriminate arrest and confrontation with security forces will continue to escalate the tension and strengthen the radical elements within the group,” said Murtala.

Additional reporting by Eromo Egbejule in Lagos