(Reuters) – Bahraini security forces killed a teenager and injured dozens more protesters on Thursday, an opposition website said, during clashes on the second anniversary of an uprising to demand democratic reforms in the U.S.-allied Gulf Arab state.

Several hundred demonstrators, mostly youths from largely Shi’ite villages, blocked roads around the capital Manama and hurled stones and fire bombs at police, who responded with birdshot and tear gas, witnesses said.

Security forces confirmed they had fired warning shots at the crowds and one young man had been killed in the protests, which began in the early morning and lasted almost all day.

The clashes were the most violent in recent months and could mar talks that began on Sunday between mostly Shi’ite Muslim opposition groups and the Sunni-dominated government to try to end political deadlock in Bahrain, which is home to the U.S. Fifth Fleet.

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