Authorities in Nigeria have extended a dusk-to-dawn curfew in Port Harcourt for a further week.

Tight controls triggered by gun battles between rival gangs have been in effect in the oil-producing city since last Friday. Nigerian troops have raided hideouts of suspected gang leaders, sparking more gunbattles.

Local newspapers say dozens of people have died in the clashes.

Nigeria's southern Niger Delta region has become increasingly lawless since militants began attacking the government and the oil industry in late 2005.

The militants are demanding that villages in the Niger Delta get more of the region's oil wealth. Criminal gangs have taken advantage of the unrest to kidnap dozens of foreign workers for ransom.

The governor of Rivers State, Celestine Omehia says troops will remain in Port Harcourt for at least six months in an effort to restore order.

Port Harcourt is the hub of the country's southern oil-producing region.

Oil production has dropped by about 20 percent since militants began attacking government and oil industry targets two years ago.

Some information for this report was provided by AFP and AP.