At least one person was killed on Monday as the police and members of the Islamic Movement in Nigeria (IMN), also known as Shiites, clashed again in Abuja.
A Channels Television reporter was also hit by a stray bullet, the station said.
The Shiites also set a sub-station of the National Emergency Management Agency (NEMA) at the federal secretariat, Abuja, on fire, after the police disrupted their protest.
Two vehicles of the agency were also set ablaze
The policemen shot at the protesters who were advancing towards the Eagle Square.
Reports are suggesting that the number of deaths in the clash could be as many as six.
The group is protesting the refusal of the Federal Government to release its leader, Ibrahim El Zakzaky, and his wife, who have been in detention since 2015.
Shiites and the police had first clashed on July 9 after they gained entrance into the premises of the National Assembly.
Nine policemen were injured in that clash.