Five Bahraini policemen were lightly injured in a "terrorist explosion" outside the capital Manama on Monday, the state news agency reported.
The agency said the blast occurred in the village of Daih on Budaiya road while the policemen were guarding a procession marking the annual Ashura festival.
The agency quoted the interior ministry as saying on its Twitter account that "the necessary steps" were being taken, without giving any details.
The explosion was the latest in a series of attacks targeting policemen in the country.
The government blames the attacks on militants.
In June, a member of Bahrains security forces was killed in an explosion in the village of Diraz, the hometown of the spiritual leader Ayatollah Isa Qassim. The interior ministry blamed "terrorists" for the attack.