Two policemen were injured, one seriously, when their patrol was attacked in Benghazi, the official Libyan News Agency (LANA) reported on Tuesday.
Unidentified assailants threw a bomb into the policemen's car Monday night. Security forces later detained the occupants of two suspect vehicles for questioning over the attack, dpa reported.
On Saturday, Italy's consul general in Benghazi, Guido De Sanctis, escaped unharmed when gunmen opened fire on his armour-plated car. It was the third attack on foreign diplomats in Benghazi in under a year.
US ambassador to Libya Chris Stevens was killed when gunmen attacked the US consulate in the city in September, while the British ambassador escaped uninjured from an attack in June.
Security officials in the city - the cradle of Libya's revolution against former leader Moamer Gaddafi - have also been targeted in recent months.
Libya is currently restructuring its security services, with the hitherto dominant Supreme Security Committees due to be disbanded and their members integrated into the police.
The committees, made up of revolutionary brigades, have played a major security role due to the weakness of the nascent police force.
But observers have criticized the inability of the Interior Ministry to control the committees and the perceived sympathy of some committees with radical Islamists.