Sana'a, Yemen - Nine policemen were wounded after an unidentified attacker threw a hand grenade at a police patrol in the southern Yemeni city of Dhalea on Monday, local sources said.

The sources told Deutsche Presse-Agentur dpa the attacker detonated the grenade as the police vehicle parked near a gathering of people protesting the delay of investigations into a murder crime that took place in the city last week.

Police arrested three suspects after the attack, the sources said.

It was not immediately known whether the attacker was one of the protesters. (dpa)