A Bahraini policeman was killed and eight others wounded on Friday in a "terrorist" bomb attack on the bus in which they were travelling, the interior ministry said.
The eight wounded policemen sustained serious to medium injuries and were admitted to hospital, the ministry said on its Twitter account.
It said the attack was carried out by a "terrorist" group which remotely detonated a home-made bomb.
The attack took place near the Shiite town of Jidhafs outside the capital Manama.
Authorities opened an investigation into the attack and police began a manhunt to find and arrest the assailants, the ministry said.
Bahrain, a Shiite-majority kingdom ruled by a Sunni dynasty, has seen sporadic violence since a crackdown in 2011 on a protest movement demanding a constitutional monarchy and an elected prime minister.
Authorities have since tightened their grip on dissent, jailing hundreds of protesters and stripping a string of high-profile activists and clerics of citizenship.
Last week, Interior Minister Sheikh Rashed Al-Khalifa accused Iran of harbouring 160 Bahrainis convicted of terrorism and stripped of their citizenship.
He accused Iran's elite Revolutionary Guards of having trained the group, who were convicted of attacks that killed 25 security personnel and wounded 3,000 others.
Bahrain is home to the US Navy's Fifth Fleet, and a British army base is currently under construction.
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