Violence has flared up in Bahrain in the wake of a leading Shia cleric's call on Friday to "crush" police.
At least one person was reportedly killed and dozens were injured as protesters attacked security forces in Shia villages outside the capital.
Demonstrators from the Shia majority have faced a crackdown in the past year, as the Sunni monarchy attempts to cope with their demands for reform.
Sheikh Isa Qassim said: "Whoever you see abusing a woman, crush him."
The sermon by the previously moderate cleric was taken as a call to arms by angry young Shia.
In a fiery harangue, a video of which has been seen by the BBC, Sheikh Qassim said: "Let us die for our honour."
"How do those who do this to people expect the people to remain silent and not defend their rights and honour?" he asked.
Video footage made available to the BBC show security forces being routed by Shia activists hurling stones and petrol bombs in the village of Sitra near the capital Manama over the weekend.
Sitra has been a focus of tension in the struggle between Shia protesters and the government of King Hamad Bin Isa al-Khalifa.
Two pictures from another Shia village, Diraz, show a security officer lying wounded on the pavement after being beaten by rioters on Tuesday.
Others show protesters in balaclavas and white martyrdom robes in a stand-off with police in Budaiya, just outside Manama.
The ministry of interior later released a statement saying that 41 security officers had been injured, two of them critically.
Activists meanwhile said at least one protester had died as a result of police violence.
Anger was stoked at the funeral on Sunday of 24-year-old Yousif al-Mawaly. Police say they found his body floating in the sea, a victim of drowning.
But his family says he was arrested, tortured and then dumped. Photographs of his body seen by the BBC appear to show abrasions and bruises consistent with beating.
Still, the level of violence has caught peaceful activists off guard.
When shown the picture of the injured policeman, one said: "No one should come down to that level. It is not right what (the protesters) are doing."
The pro-democracy activist said the violent response has been well organised.
He said "thousands" of petrol bombs were being prepared by protesters for use against security forces.
Sheikh Qassim's comments have been condemned by the government as irresponsible.