Shia protesters and police clashed in Bahrain on Friday following the funeral of a prisoner who died while serving a 15-year sentence for taking part in anti-regime demonstrations, witnesses said.

The interior ministry of the Gulf state had announced on Twitter Thursday the death of the 45-year-old, saying he died while exercising at Jaw prison south of Manama.

It attributed Mohammed Sahwan's death to natural causes, but relatives claimed he died as a result of injuries sustained during the crackdown in 2011 of the Shia protest movement calling for reforms to the Sunni monarchy.

His relatives said Sahwan's head and body still contained buckshot from injuries sustained during the protests six years ago.

After Friday's funeral in Sanabes village near the capital, demonstrators tried to march on the site of the Pearl roundabout, the epicentre of the 2011 protests.

Police fired buckshot and tear gas to disperse them, the witnesses said.