Several policemen were injured when a home-made bomb exploded at a roundabout west of Bahrain's capital Manama, the prime minister said.
Sheikh Khalifa bin Salman Al Khalifa said the explosion happened at Budaiya motorway "leaving a number of policemen injured whilst on duty", the Bahrain News Agency said.
A ministry of interior message on Twitter put the number of wounded at three and described the device as remotely-detonated and home-made.
Both the ministry and Sheikh Khalifa described the explosion as a "terror" incident.
Bahraini police say they have been the target of numerous attacks with home-made bombs since April 2012, including one that killed a policeman in October.
The Sunni-dominated government has been struggling since early last year to end unrest led mainly by the kingdom's majority Shiite Muslims.
Five home-made bombs killed two people in Bahrain on November 5, and the government said the attacks bore the hallmarks of Hizbollah, the Lebanese militant group allied with Iran. Iran dismisses Bahraini accusations of involvement in the political unrest. Hizbollah also denies involvement, but has criticised the government's handling of protests.
Sheikh Khalifa said that Bahrain would remain stable and its citizens "would foil any terror plot targeting Bahrain to subvert its security", BNA reported.