Rights group Amnesty International on Monday called on Bahrain to free the country's most prominent opposition figure, a day ahead of an expected verdict on charges of inciting violence against the ruling system.
Sheikh Ali Salman, a Shi'ite Muslim cleric and head of the opposition al Wefaq Islamic Society, was arrested in December in a case that angered his followers and stirred unrest in the Gulf Arab state.
The prosecution accuses Salman of promoting the overthrow of the political system by force, inciting violence and supporting attacks that caused the deaths of 14 policemen.
Amnesty said it considered Salman "a prisoner of conscience detained solely for peacefully expressing his views."
"The detention and trial of Sheikh Ali Salman is a blatant violation of his right to freedom of expression and demonstrates the Bahraini authorities' continued attempt to suppress political opposition and silence critical voices," it said.
There was no immediate comment by Bahrain officials on the report. Authorities have previously denied the trial was politically motivated.
Salman and his supporters deny the charges and have dismissed the trial as bid to muzzle dissent. If convicted, the 49-year-old faces up to 10 years in jail, his defence team says.
He also faces three other, lesser charges, including inciting hatred and insulting the Interior Ministry.
Bahrain, which hosts the U.S. Fifth Fleet, has experienced sporadic unrest since mass protests in 2011, led by majority Shi'ite Muslims demanding reforms and a bigger role in government.
The Sunni-ruled kingdom says it has made strides in political reform and increasing oversight on security forces, but opponents and rights groups say abuses continue.
As a political accord remains elusive, Bahrain has seen an increase in deadly bomb attacks on the security forces.