Bahraini police said they arrested several suspects in a Shiite village on Thursday following an attack the night before in which two policemen were badly burned when they were attacked with petrol bombs.
"The attack happened around 9:00 pm, when a group of men armed with petrol bombs attacked a police patrol in Sitra," said a statement from the information affairs authority, quoting the director general of police.
"The police jeep was damaged and two policemen were seriously injured with severe burns. They were referred to hospital for treatment and are still in critical condition."
The official said police arrested several people involved in the attack and referred them to the public prosecutor.
The incident came as violence raged a day after police dispersed protesters attempting to march on the capital's former Pearl Square, the focal point of a February 14, 2011 pro-democracy uprising that was crushed a month later.
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Meanwhile, Al-Wefaq, the principal Shiite Muslim opposition group in the Sunni-dominated kingdom, denounced the arrest of some 20 people in Sitra on Wednesday night.
It said security forces, deployed heavily in the village, fired tear gas and percussion grenades into people's homes to "punish their inhabitants for their political ideas."
On Wednesday, UN Secretary General Ban Ki-moon expressed concern over recent violence between security forces and demonstrators, urging authorities there to exercise "maximum restraint."
"The secretary-general is concerned about reports of clashes in Bahrain between security forces and demonstrators over the past few days," Ban said in a statement issued through his office.
The UN leader called for "a genuine, all-inclusive and meaningful dialogue that meets the legitimate aspirations of all Bahrainis," which he said would "promote peace and stability in the country."
Last year's crackdown left 35 people dead, according to an independent commission of inquiry into the violence.