Seven Bahraini policemen have been injured in a "terrorist attack" by unknown assailants in the Shiite village of Akr, south of the capital Manama, a top security official has said.
General Tareq al-Hassan, Bahrain's public security chief, said an improvised bomb exploded late Monday near a police checkpoint at the entrance to the village, "wounding seven policemen, three of them critically," Bahrain's official BNA news agency reported.
Al-Hassan added that the initial investigation has "revealed that the explosion was caused by a pipe bomb attached to a container full of gasoline."
The main Shiite opposition group, Al-Wefaq, said in a statement that it was closely "following the developments in Akr... but we have no independent information" about the incident, adding that the village was "entirely surrounded by security forces who are imposing collective punishment."
"We have received calls for help from village residents," Al-Wefaq said in a statement released late Monday adding that security forces are "using pellet guns" against the villagers.
Demonstrations in Bahrain's Shiite villages have increased in recent weeks as tensions between the authorities and the opposition escalate over the fate of a jailed Shiite activist who has been on a hunger strike for two months.
Abdulhadi al-Khawaja, was condemned with other opposition activists to life in jail over an alleged plot to topple the Sunni monarchy during a month-long protest a year ago. He began a hunger strike on the night of February 8-9.
Front Line Defenders, a Dublin-based NGO, has warned that Khawaja could die in jail.
Monday's explosion coincides with mounting pressure by the Shiite opposition on Grand Prix organisers to cancel the Formula One show for a second year in a row.
The youth group of the "Revolution of February 14" has called for "three days of rage" in the Gulf kingdom from April 20 to 22, and also launched a campaign on Twitter to prevent the race which is scheduled for April 22.