A blast injured four on-duty policemen in the northwestern Bahraini town of Bani Jamra, Chief of Public Security Major-General Tariq Al Hassan said.
The explosion, caused by a homemade device with a remote detonator, occurred at 12:33 a.m., Al Hassan said in an e-mailed statement from Manama, the capital. One of the officers is in a critical condition, while the others sustained serious wounds and burns, he said.
Bahrain quashed a month of mass rallies last year by mostly Shiite demonstrators demanding equal rights and political representation. Small rallies still take place regularly in Shiite neighborhoods, sometimes spilling into commercial areas of Manama.