Three policemen have been killed in a bomb explosion in Bahrain, the interior ministry has said.
A post on Twitter said the officers had been "dispersing rioters" in the village of Daih, west of the capital, Manama, at the time of the attack.
Witnesses reported hearing a blast during clashes between anti-government protesters and police who were firing tear gas and birdshot to disperse them.
Thirteen police officers have now been killed since protests erupted in 2011.
Last month, one was fatally injured by an explosion on the third anniversary of the start of the uprising that has seen people take to the streets to demand more democracy and an end to what they perceive as discrimination against the Shia community by the Sunni royal family.
Following Monday's explosion, six leading opposition groups issued a joint statement saying they "regretted casualties, regardless of which side they belonged to".
"The sanctity of blood applies to every human being," it added.
The statement called on opposition supporters to "adhere to peaceful means, and condemn and disclaim criminal acts" and on security forces to "exercise restraint".
The interior ministry said the "terror blast" happened after "police dispersed a breakaway group of thugs who diverted from a funeral route in Daih to riot".
Earlier, people had gathered in the predominantly Shia village for a third day of funeral processions for a detainee who died in hospital last week.
The government and prosecutors said Jaffar Mohammed Jaffar died as a result of complications caused by sickle cell anaemia, which caused a clot to form in his lungs.
But the main Shia opposition group, Wefaq, alleged that he had been tortured in custody and denied adequate medical care.
His family said he had been subjected to beatings and electrocution since his arrest in December in connection with a seizure of weapons.
Opposition and human rights activists say that in addition to the 13 policemen, more than 80 civilians have been killed over the past three years. However, the government says the death toll is lower.