Anti-government protests flare up in the streets of Bahrain, after a court handed a rare death sentence to two Shi'ite Muslim men for plotting a bomb attack that killed a police officer in February.

A third was sentenced to life in prison.

The ruling came a day after authorities detained Sheikh Ali Salman, the head of the country's main Shi'ite opposition group al-Wefaq, for unspecified violations.

His photograph is carried by many Shi'ite demonstrators who call for greater social, political and economic equality in the Sunni-led country.

Sporadic protests have erupted in the Western-allied kingdom since 2011.

The court ruling is subject to appeal.