Nigerian troops are patrolling Port Harcourt, the capital of the country's volatile oil region Saturday to forestall fresh violence a day after rival gangs clashed. Gun battles involving cult groups killed dozens last August. For VOA, Gilbert da Costa has more in this report from Abuja.

Locals drive past smoke from a Shell oil pipe line near the oil rich city of Port Harcourt (File)

The gangs at the center of the violence confiscate oil in the Niger Delta by vandalizing oil pipelines. They are known as cult gangs because they administer traditional oaths of loyalty to their members.

As well as fighting with the security forces, they fight among themselves for the control of the water ways that give access to the oil wells and facilities.

Some gangs may also be involved in the kidnappings of hundreds of foreigners, mostly oil workers, who have been abducted since the groups began their campaigns in early 2006.

Port Harcourt-based reporter Mike Tamuno told VOA some residents were hurt in the shootout. "There was shooting yesterday in the Waterside area of Port Harcourt. It was a clash between two rival cult groups.So far, both the police and joint military task force say nobody was killed, but several residents received bullet wounds," he said.

Human rights activists say that like many militias in the delta, the warring gangs in Port Harcourt were at various times sponsored by politicians who used them to rig elections or scare opponents.

Port Harcourt is the biggest city in the oil-producing Niger Delta and oil companies, including  Royal Dutch Shell, have offices there. It is also home to two of Nigeria's four refineries.

Nearly two decades of unrest in the oil-rich Niger Delta have in recent years evolved into an armed insurgency for local control of the region's oil wealth.