"The area has been calm. There has been no more fighting since last week," army spokesman Colonel Chukwuemeka Onwuamaegbu told AFP.

But officials from US giant ChevronTexaco and the Anglo-Dutch group Shell said they had no immediate plans to return to their evacuated facilities in the delta.

The firms began to shut down their operations three weeks ago after an uprising by ethnic Ijaw militants in the swamps south and west of the oil city of Warri triggered violent clashes with security forces.

Nigeria is now losing more than 40 percent of its daily production, some 800,000 barrels per day, and the shut down is being closely followed by oil traders already worried by the war in Iraq.

At least 13 people, including eight soldiers and navy personnel, have been killed, according to military officials.

Refugees from the region have spoken of scores of casualties in Ijaw attacks on the neighbouring Itsekiri ethnic group. ChevronTexaco has evacuated 1,600 Itsekiri villagers from villages near its main terminal.

An AFP photographer who flew over the area last week in a helicopter saw at least two villages had been attacked and burned.

The Ijaw have threatened to destroy the abandoned oil facilities if their demands for greater political representation are not met in time for Nigeria's April 12 legislative and and April 19 presidential elections.

But a local Ijaw leader, who asked not to be named, told AFP by telephone from a delta village that calm had returned.

"There's a sort of truce, and political discussions are going on," he said. "The oil companies should be able to return next week."

A large force of army troops and naval patrol boats has been deployed to protect the industry, but on Wednesday the majors played down the idea that they might make a rapid return.

"We will resume production when it is safe to do so," said a spokesman for Shell.

Shell evacuated its workers from the troubled area when the violence broke out and has has reported a loss of 320,000 barrels per day in the Warri area while 50,000 barrels was cut in its eastern operation area.

Chevron's Nigerian subsidiary said it has yet to return to work.

"The situation is still the same. We are monitoring events to determine the best and safest time to return," a spokesman told AFP.

ChevronTexaco shut down the huge Escravos oil export terminal in the western delta, accounting for some 440,000 barrels per day in output.

French firm TotalFinaElf, which also evacuated the area and shut down oil wells, is losing 7,500 barrels daily to the unrest.

Last week, President Olusegun Obasanjo promised to ensure peace in the region.

"Right now we are working with the inspector general of police, chief of army staff and chief of naval staff, to calm the situation and get the culprits," he said.

SPACE.WIRE