Updated

Riot police in Bahrain have fired tear gas during street clashes with anti-government protesters in the heart of the Gulf kingdom's capital Manama.

The demonstrations by Shiite-led groups Friday are part of attempts to challenge authorities by reviving opposition marches in the commercial center of the strategic nation, which is home to the U.S. Navy's 5th Fleet. Marches in central Manama were common in the first months of the uprising that began in February 2011, but were mostly pushed to the outskirts by a security crackdown.

More than 50 people have been killed in 19 months of unrest. Majority Shiites seek a greater political voice in the Sunni-ruled nation.