Nigerian troops are continuing their crackdown on gangsters in Port Harcourt, the main oil city in the southeastern Rivers State. For VOA, Gilbert da Costa reports that residents are terrified at the prospect of more violence.

The army and police appear to have regained full control of Port Harcourt days after the government imposed a dusk-to-dawn curfew to check gun fights across the restive city.

State police commissioner Felix Ogbaudu says the city is now calm.

"Everything is very calm, nothing is happening. We've not had a single shot since Thursday, and we intend to sustain it," he said.

Local newspapers reported some 40 deaths in fighting between troops and heavily armed gangs last Thursday.

Decades of simmering tensions in the oil-rich Niger Delta have evolved into an armed insurgency, which the ill-equipped and poorly-paid security forces are struggling to contain.

Analysts say the lack of resources is hampering the capacity of the federal government-controlled security agencies to deal with the insurgents.

Rivers State spokesman Emma Okah says the state government is now saddled with funding the cash-strapped defense forces.

"On a monthly basis, we spend a minimum of 35 million naira [$300,000] to provide for logistics and assist the armed forces to do their work because of the volatile nature of the area," said Okah. "The Nigerian air force aircraft cannot fly if the Rivers State government does not bring money to maintain and fuel. These have been happening for some years now."

The criminal gangs are widely believed to have been sponsored, initially, by politicians who used them to intimidate opponents and rig elections.

The gangs have grown rich and powerful by stealing oil from the region's network of pipelines.

Port Harcourt is the oil capital of Nigeria and several oil companies operate from there. It is also the base of two of Nigeria's four oil refineries.

Foreign oil workers have been targeted by gunmen demanding ransom for their release. More than 200 people have been kidnapped in the past 18 months, and armed robberies are increasing.

The head of Nigeria's powerful oil workers union, Peter Esele, says the attacks have forced thousands of foreign workers to flee the region as well as the closure of some operations in Port Harcourt.

"You have companies now moving out of Port Harcourt. There are series of companies that are moving out of Port Harcourt, even some are leaving the country and others are moving to Lagos. Again, what assurance do you have that," said Esele.  "Yesterday it was Warri, today it is Port Harcourt and who knows, tomorrow it may be Lagos. So it is left for the government to nip all these things in the bud [correct the problem] before everybody is consumed."

President Umaru Yar'Adua, who took office in May, has pledged to address the region's grievances, but Niger Delta watchers say the violence appears to be spiraling out of control.