There have been violent clashes outside Nigeria's National Assembly between police and Shia protesters.
Protesters say officers shot two people dead, but the police said they had used "minimum force" and that eight security personnel were injured.
The members of the pro-Iran Shia Muslim sect, the Islamic Movement of Nigeria (IMN), were protesting against the detention of their leader, Sheikh Ibraheem Zakzaky.
He has been detained since 2015.
The police said that two of their officers had been shot in the leg and six others injured by clubs and stones.
They added that 40 members of the sect had been arrested.
IMN member, Abdullahi Muhammad Musa, told Reuters that police opened fire, killing two protesters, as they tried to enter the assembly building peacefully.
Sheikh Zakzaky's followers have been protesting regularly since he was arrested in the aftermath of clashes between his followers and the army.
The army had accused his followers of attempting to assassinate the chief of army staff, which the IMN denied.
The army killed 347 members of the IMN in those clashes, whereas one soldier was killed, a judicial review found.
Sheikh Zakzaky made his first public court appearance since he was arrested in May 2018 in Kaduna High Court in north-west Nigeria. The case continues.