A backpack containing dynamite and nails exploded during a celebration in a southern Peruvian market, killing six people and wounding 48, police said Saturday.

Police Col. Romeo Delgado told The Associated Press by telephone that police have not ruled out a terrorist attack.

"What the police have to determine is the motive, the aim, and what kind of criminal did it," he said.

The explosion occurred around 10:30 p.m. Friday in the Andean city of Juliaca, 520 miles southeast of the capital, Lima, Delgado said.

This week marks 27 years since the Maoist Shining Path movement's first armed attack.

On May 17, 1980, the group burned ballot boxes on the eve of Peru's presidential election in a village in the highland Ayacucho department.

The insurgency almost brought Peru's government to its knees in the 1980s and early 1990s with a campaign of massacres, political assassinations, bombings and sabotage.

Since the 1992 capture of Shining Path founder Abimael Guzman, the group has been reduced to a few hundred guerrillas who stage sporadic ambushes on security forces and provide protection to cocaine traffickers.