A homemade bomb exploded Sunday near Manama after police rounded up 22 people suspected of attacking security forces and blocking roads during protests, including in the lead-up to its Formula One race this month, police said.
"An explosion targeting a police patrol carrying out its duties ... near (the Shiite village of) Dia was carried out using a homemade bomb on Sunday morning," said a police statement on the official BNA news agency.
No casualties were reported in the attack that only damaged the police vehicle, according to the statement which said an investigation was underway.
The announcement came after another police statement on BNA late Saturday said that arrests were made in Shiite villages in connection with alleged acts of violence since late February.
In one case, police detained six people suspected of participating in a March 7 "terrorist attack" on police patrols in the village of Maqaba, west of the capital Manama, it said, adding security forces were still searching for other suspects.
Others were arrested over alleged attacks on police with petrol bombs and metal rods.
Police also arrested two people suspected of blocking roads and setting tyres ablaze in the area of Dair, close to the airport, on April 14, when Shiite demonstrations intensified against Bahrain hosting the Formula One Grand Prix race on April 21.
It was unclear when all of the arrests were made.
Al-Wefaq, the main Shiite opposition formation, said on Saturday that police arrested 14 people during raids on Thursday and Friday.
Shiite youths frequently clash with police in villages surrounding Manama. In some cases they hurl petrol bombs and burn tyres, while police fire tear gas and buck shot to disperse them.
The Shiite Muslim-majority kingdom, ruled by a Sunni dynasty, was rocked by a month-long uprising in 2011, crushed with the help of Gulf troops led by neighbouring Saudi Arabia.
Strategically located just across the Gulf from Iran, Bahrain is home base to the US Navy's Fifth Fleet and is also a major offshore financial and services centre for its Arab neighbours in the oil-rich Gulf.