Bahraini police and anti-government protesters clashed in Shiite villages, leaving dozens of officers and several demonstrators injured, officials and the opposition said Wednesday.
The interior ministry accused protesters of "orchestrated attacks on police forces... across the kingdom" that caused "significant injuries" to 41 officers, two of them requiring "critical care" at Bahrain's military hospital.
An opposition figure said protesters clashed with security forces in at least four Shiite villages, leaving several of them injured, including one seriously after being hit on the head with a tear gas canister.
Earlier, Public Security Chief Major General Tariq al-Hassan said that "vandals blocked roads" and threw petrol bombs during the clashes on Tuesday night.
Hassan, who was quoted by the official BNA news agency website, said security forces had made "several arrests" in Shiite villages, but gave no further details.
Former opposition MP and Wefaq member Matar Matar, who gave the civilian injury toll, said two protesters have been killed in recent months from tear gas injuries to the head.
"This indicates the existence of a (government) policy to intentionally injure protesters rather than just merely disperse them," Matar told AFP.
On December 31, Al-Wefaq said 15-year-old Sayyed Hashem Saeed died after being hit in the head by a tear gas canister.
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The government at the time released a statement saying they would investigate the teenager's death.
According to Matar, Tuesday night's clashes erupted after posts on social networks, including Facebook and Twitter, called on Bahrainis to go out and "confront" the security forces.
Al-Wefaq has posted videos and pictures of the unrest on its Facebook page, including images of police officers in the Shiite villages of Sitra and Bani Jamra, dressed in full riot gear and hurling objects, including metal rods, at a small crowd of young men.
In another image posted on the page, plumes of tear gas can be seen wafting through the night skies over the Shiite town of Bani Jamra.
On Monday, the United States said it was relocating embassy staff and their families to new neighbourhoods in Bahrain's capital Manama as part of safety precautions amid anti-government unrest.
A crackdown on Shiite-led protests in mid-March last year led to the deaths of 35 people, including five security personnel and five detainees tortured to death, a commission appointed by the king to investigate the unrest said.
Tensions have remained high in Bahrain since the initial crackdown last spring, and sporadic violence has risen in recent weeks as the first anniversary approaches of the launch of the protests against the government.
Bahrain's Shiite community, although a majority in the kingdom ruled by the Sunni Al-Khalifa dynasty, has complained of marginalisation.