The demonstration in support of Sheikh Isa Qassim shows the unrest gripping the tiny island of Bahrain, sparked by an intense government's crackdown on opposition groups and dissent, on a level unseen since its 2011 Arab Spring protest.
But while the protests five years ago saw the island's Shiite majority and others rise up to demand more political freedom from its Sunni rulers, this crackdown has seen a growing level of sectarianism.
"The country now has been divided and you have to say the government bears a lot of responsibility," said Brian Dooley, the director of the Washington-based group Human Rights First.
"The targeting of the theological side of things, I think, is particularly worrying."
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The government in Bahrain, which is home to the U.S. Navy's 5th Fleet, crushed the Arab Spring protests with the help of troops from Saudi Arabia and the United Arab Emirates. Since then, the island has seen low-level unrest, protests and attacks on police.
His case is the latest in a string of incidents since Bahrain's Defense Force announced in April it was "ready to deal firmly and with determination with these sedition groups and their heads" after a gasoline bomb killed a police officer.