"Four policemen injured including one critically in a terror blast in Bani Jamra," west of the capital Manama, , the kingdom's interior ministry said on Saturday on Twitter, without giving further details of the attack or its perpetrators.

Ministry officials were not immediately available for comment.

Tensions are running high in Bahrain where a month-long uprising led by the Shiite-majority population was crushed in March 2011. Demonstrations have, however, intensified in recent months as protesters sporadically clash with the police.

Amnesty International says around 60 people have been killed since the protests first erupted against the Sunni-ruled kingdom in February last year.