Villagers are fleeing the conflict

Shell, Nigeria's biggest oil producer, said it had been forced to evacuate four facilities in the coastal swamps amid fears of attacks by ethnic militants.

The closures will bring the company's loss in production to 320,000 barrels a day.

Violent clashes between the Ijaw ethnic militants and the Nigerian security forces have been raging for the past 11 days.

The Ijaw group has warned it would destroy evacuated oilfields if its demands for greater political representation were not met.

Bunkering

Shell said its decision to evacuate its premises was part of "precautionary and security measures".

We have the oil facilities at our disposal and we will do very funny things with them if the government does not look into the root of the matter Kingsley Otuaro, secretary of the Federation of Delta Ijaw communities

It also revealed that it is losing a further 50,000 barrels per day because of unrelated illegal bunkering - loading barrels onto cargo ships illegally - in the east Niger Delta.

The closures follow the decision by US producer ChevronTexaco to shut its main Nigerian export terminal, Escravos, at the weekend after one of its workers was shot dead in the fighting.

France's TotalFinaElf has also pulled out of an oil storage farm that was attacked by militants.

The total loss in production now stands at about 767,500 barrels a day - more than a third of Nigeria's usual daily exports.

Ijaw threat

The bloody protests have caused further jitters in world oil prices amid fears that the conflict in Iraq will disrupt supply.

London's Brent crude futures prices were up $1.30 at $26.65 on Monday, which traders attributed to a number of factors.

"The price rise is due to.....Saddam's speech earlier, the closure in Nigeria and a bit of short covering as well," said one London trader.

Kingsley Otuaro, secretary of the Federation of Delta Ijaw communities, said: "We have the tank farms and oil facilities at our disposal and we will do very funny things with them if the government does not look into the root of the matter."

Shell is the largest foreign investor in Nigeria with capacity of over one million barrels per day.