DOUALA, Cameroon (AP) _ About 15 decaying corpses wrapped in plastic lay Tuesday in an unexplained mass grave on the outskirts of a western port city in this central African nation.

The bodies were dumped in an unmarked pit in the city's main graveyard. The corpses were partially decomposed and it was not clear how the people had died.

Local witnesses, speaking on condition of anonymity for fear of retribution, said men in civilian clothes had buried about 100 more bodies over numerous days and nights in the same spot about a month ago. The exposed bodies were dropped on top of the buried ones about two weeks ago.

Government officials could not be reached for comment Tuesday and have made no public statement about the grave, which local journalists said was discovered over the weekend. There was no indication that investigators had visited the site.

Douala has become increasingly violent in recent years, with carjackings and burglaries becoming commonplace.

In addition, the Roman Catholic Church and opposition leaders have accused a paramilitary unit _ set up in February to fight the mounting crime _ of extra-judicial killings. Force members are authorized to shoot on sight if they catch someone committing an offense.

The government launched a major anti-crime crackdown after the large expatriate French community reacted with anger and alarm following the killing of a well-known French butcher.

The crusade has since widened to other parts of the poverty-wracked country, with anti-crime squads stepping up patrols in high-risk areas.