ABUJA, Nigeria (AP) — Nigerian police fired tear gas Thursday to disperse anti-government demonstrations by Shiite Muslims in the capital, Abuja, and the northwestern city of Kaduna.

The protesters were demanding the release of Shiite leader Sheikh Ibrahim Zakzaky, who has been jailed since 2015. The protests have been gaining momentum this week following reports that Zakzaky is in failing health.

In Abuja, about 50 demonstrators at Eagle Square were dispersed after tear gas was fired. In Kaduna the demonstration was also broken up by police firing tear gas and gunshots were heard.

Earlier this week protesters invaded Nigeria's parliament building to demand the release of Zakzaky. Many demonstrators were arrested and 38 appeared in court Thursday and were charged with unlawful assembly and destruction of public property. All pleaded not guilty.