A truck packed with explosives blew up Friday in a crowded business section of the Afghan city of Jalalabad, killing 31 people and damaging cars and buildings, the state-run Kabul radio reported.

It was the third car bomb attack in an Afghan city in as many days.

The radio, quoting Afghanistan's official Bakhtar news agency, said the blast also destroyed 25 vehicles parked in a nearby parking lot and damaged a local theater and 45 shops.

Kabul radio, monitored in Islamabad, blamed "criminal extremist opposition" for the explosion, apparently referring to Afghan guerrillas fighting the pro-Soviet government. It called the attack an "unforgivable crime."