Manila - Four people were killed and 11 injured in a grenade attack by communist rebels on a bakeshop in a southern Philippine town Thursday, officials said.

Major Armand Rico, a regional military spokesman, said the grenade was lobbed at the Park and Go Bakeshop in Nabunturan town in Compostela Valley, 930 kilometres south of Manila, before dawn.

Rico said communist rebels were believed to be behind the attack.

"The motive is believed to be the bakeshop's non-payment of revolutionary taxes demanded by the guerrillas," he said.

Provincial Governor Arthur Chiongky Uy said four people - one policeman, two students and a driver - were killed in the attack.

He offered a 200,000-peso (4,450-dollar) cash reward for information that would lead to the arrest of the perpetrators.

Communist rebels have in the past attacked companies and business establishments that refuse to pay revolutionary taxes, which have become a major source of their funds.

The guerrillas have been fighting the Philippine government since the late 1960s, making the movement one of the longest-running leftist insurgencies in Asia. (dpa)