Filed at 1:03 p.m. ET

PORT HARCOURT, Nigeria (AP) -- Dozens of villagers have been killed, many hacked to death, in three days of clashes between rival political factions battling for influence in an oil-rich area of the Niger Delta, activists and witnesses said Tuesday.

Thousands of refugees fleeing the mayhem in Nembe town were still arriving Tuesday in neighboring communities in southeastern Bayelsa state, after a weekend of violence. They included a woman who apparently escaped by swimming across the river after suffering gunshot wounds.

Dozens of homes and businesses were razed.

The fighting erupted July 20 between members of the Tama Boys and Isoungufuro, rival gangs led by local politicians Nimi Barigha Amange and Lionel Jonathan. Both men want to contest local Aug. 10 elections under the banner of the ruling Peoples Democratic Party.

The clash apparently came in response to an earlier round of fighting between the two factions that disrupted July 5 party elections called to decide local candidates. At least 20 people were killed in that initial outburst.

The latest bloodletting lasted nearly three days before subsiding on Sunday night, when Bayelsa police commissioner Udon Ekpoudon said squads of heavily armed police were deployed to restore calm.

Ekpoudon could not provide casualty figures, although witnesses and political activists who visited Nembe Monday spoke of seeing more than 30 decaying bodies littering town streets.

Activists included Robert Azibaola, president of the Niger Delta Humanitarian and Environmental Rights Organization. Other witnesses spoke to The Associated Press on condition of anonymity for fear of reprisals.

Both sides in the fighting accused the other of having curried the favor -- and financial backing -- of several multinational oil companies that drill for crude nearby.

The oil firms have denied a role in political violence, which regularly flares in the Delta.

Political races in the Niger Delta frequently erupt in violence among politicians grappling for control of government oil revenues and payoffs by oil firms. Despite the oil riches pumped from beneath Niger Delta marshes and rivers, it remains one of Nigeria's poorest areas.

Nigeria is the world's sixth-largest oil exporter.

The violence was not directly related to this month's all-women takeovers of ChevronTexaco installations in the Niger Delta.

Nigeria is frequently riven by political, ethnic and religious violence. Fighting has escalated since President Olusegun Obasanjo's 1999 election ended decades of brutal and corrupt military rule.