Bahraini security forces fired birdshot and tear gas to disperse protesters in Shiite villages around the capital, witnesses said on Tuesday, as police announced the arrest of 11 "saboteurs".
Several protesters were wounded as police dispersed demonstrations overnight that were called by the "Youth Coalition of February 14" to mark the Sunni-ruled, Shiite-majority Gulf state's independence, witnesses said.
The number of casualties was difficult to assess, as protesters stay away from hospitals for fear of being arrested.
The interior ministry said: "Several areas of Bahrain witnessed riots and vandalism and attempts to block vital roads."
An "illegal demonstration" took place in the village of Bani Jamra where protesters hurled "petrol bombs and metal rods," it added.
"Security forces managed to arrest 11 saboteurs, who are currently being referred to the public prosecution."
The ministry also said that a group of "saboteurs" used petrol bombs to attack a car being driven by a woman, at the entrance to the Shiite village of Abu Saybi.
Sporadic demonstrations in Shiite villages have intensified since last year's crackdown, which ended month-long protests dominated by Shiites in the capital Manama.
Bahrain won independence from Britain on August 15, 1971.
But the kingdom, which is ruled by the Sunni Al-Khalifa dynasty does not celebrate independence. Instead, it observes the coronation of former ruler Isa bin Salman Al-Khalifa as National Day.
Meanwhile, Bahrain's public prosecution said the number of people detained over protests since Februrary 2011 had reached 923, contesting a claim by the Shiite opposition that 4,500 people were arrested.