Four policemen were wounded by an explosion in a village in western Bahrain that the government called a "terrorist" act.
"A terrorist explosion targeted security forces that were escorting firefighters... on their way to the scene" of a blaze in the village of Diraz, BNA, national broadcaster reported, citing a senior police official.
The official said "four policemen were wounded" in the explosion, adding that "two of the officers suffered serious injuries".
Diraz is a village outside the capital Manama where there have been frequent pro-democracy protests by the majority Shia Muslim community against the minority Sunni monarchy.
Witnesses at the scene said security forces imposed a total lockdown on Diraz following the explosion, shutting off all routes out of the village.
The exact cause of the blast was unknown, but "an act of sabotage" sparked the fire at a shop, the official said, adding that an investigation was launched into, what he called, the "terrorist act".
On April 9, seven policemen were wounded, three of them seriously, when a home-made bomb exploded during a protest near Manama calling for the release of Abdulhadi al-Khawaja who has been on a hunger strike which is entering its 77th day.
Tensions have been running high particularly because of the Formula One grand prix that took place last weekend.
The Bahraini government had hoped the race would be a sign that things were returning to normal, after more than a year of unrest.
The daughter of the jailed hunger striker was remanded in custody for seven days for protesting during last week's Formula One race, her lawyer said on Tuesday.
Zainab al-Khawaja was arrested on Saturday after she sat on the highway running past Bahrain's financial district during days of Shia protests held to embarrass the kingdom's rulers at a time when the race drew international media attention.
International rights groups have called for the release of her father Abdulhadi al-Khawaja and 13 other protest leaders in jail for their role in last year's pro-democracy uprising.
An appeals court on Monday delayed the men's case to April 30, prompting Amnesty International to accuse the authorities of playing with Khawaja's life. The government says he is in good health in a military hospital.
Tuesday's protests followed clashes a day earlier between police and protesters during the funeral procession of 36-year-old Salah Abbas Habib, who was found dead over the weekend.
Riot police fired tear gas to disperse protesters as they approached Pearl Square, the epicentre of last year's uprising against the Bahrain government.
The small group of protesters had broken off from a larger rally in the village of Jidhafs, where hundreds marched in support of Khawaja, demanding his release.
Foreign governments, rights groups and media watchdogs have criticised Bahrain for its handling of the protests and the slow pace of reforms.
Following the public relations debacle over the Grand Prix, the government said on Monday it had appointed a new minister of state for information affairs.