A bomb explosion has wounded four members of Bahrain's police force - two of them seriously - during clashes with protesters, officials have said.
Police said the injured men had been protecting firefighters investigating a blaze inside a shop in the mainly Shia village of Diraz on Tuesday night.
During the operation a "terrorist" bomb was detonated nearby, they added.
Tensions have been rising over the worsening condition of an imprisoned activist who has been on hunger strike.
Abdulhadi al-Khawaja is protesting against the life sentence he received from a military court in June for allegedly plotting against the state.
'Empty hospital room'
Mr Khawaja's wife, Khadija, told the BBC that she had not been able to speak to him by telephone as usual on Tuesday.
She said she had spoken to the ward sister at the Bahrain Defence Forces Hospital on Wednesday morning who told her that Mr Khawaja was not in his bed and his room was empty.
Mrs Khawaja was advised to call the interior ministry, which said it would be in contact. However, she said this had not yet happened.
Later, the interior ministry wrote on Twitter: "Abdulhadi al-Khawaja is in good health despite rumours. He is in hospital receiving full medical care."
Meanwhile, the family of an anti-government protester who was found dead on a makeshift garage roof in the village of al-Shakoura on Saturday told the BBC that a doctor who had examined his body independently had found evidence that he had been beaten.
The official death certificate said the cause of Salah Abbas Habib's death was "internal bleeding and gunshot wounds".
In addition to buckshot wounds, the doctor found a broken neck, fractured skull, three broken ribs, a dislocated shoulder and injuries to the spleen. He also found scrape marks on his body, suggesting it had been dragged.
The doctor listed the possible causes of death as the injuries to the head, lungs, spine and spleen, and not gunshot wounds.
Bahrain's interior ministry has already said it is launching an investigation into the death of Mr Habib, who reportedly took part in protests on Friday night but fled after police arrived to disperse protesters and chased him.
Activists and human rights groups accuse Bahrain's security forces of using excessive violence against demonstrators.
At least 60 people are said to have been killed since protests erupted last year demanding more democracy and an end to discrimination against the majority Shia Muslim community by the Sunni royal family.