Royal Dutch Shell has evacuated four oil facilities in Nigeria in response to a sudden intensification in the militia violence which plagues the western delta.

The withdrawal of 326 staff and contract workers from the remote flow stations in the swampy region comes after the centres were shut down following a bomb attack on the pipeline linking them to the main export terminal last week.

The evacuation will delay repairs to the pipe which carries 106,000 barrels a day, around 10 per cent of Shell's oil output from Nigeria. The move has raised fears that international companies may permanently quit the turbulent delta area if the Government, a key Western oil ally, fails to rein in the militias.

Industry sources say that Shell is considering further evacuations although the company today said that it has no plans for a wider pull-out.

The withdrawal, combined with Iran's threats to force up prices in response to threatened sanctions over its nuclear programme, prompted a rise in the cost of oil, up 93 cents to $63.18 a barrel this morning.

Royal Dutch Shell has been in a long-standing dispute with impoverished locals who accuse the company of failing to invest in their region, where an estimated 20 million people live in poverty alongside the multi-billion-dollar oil industry.

Heavily armed members of the Ijaw ethnic group killed at least one person and injured ten others on the Benisede flowstation in Bayelse State in an early-morning raid on a Shell Petroleum Development Company (SPDC) platform yesterday, the fourth such attack in five days.

The attackers invaded in speed boats, set fire to two houseboats used as staff accommodation and smashed part of the processing facility before fleeing.

In an e-mail statement, the Movement for the Emancipation of the Niger Delta, also believed to be behind the kidnapping of four foreign oil workers last week, said that it had 5,000 fighters and was intent on crippling the local activities of the world's eighth largest oil exporter. "Our aim is to totally destroy the capacity of the Nigerian government to export oil," it said.

Shell, which has 12,000 workers in Nigeria, has addressed its concerns to President Olusegun Obasanjo's Government which will be under further pressure to crack down on the indigenous militia who are demanding more control over the region's oil revenues.

The Government has yet to launch a military assault, fearing for the safety of the four foreign workers - a Briton, American, Bulgarian and Honduran - who were kidnapped from an offshore oil platform on Wednesday last week.

A spokeswoman for Shell said: "Following the growing insecurity in the area, SPDC has commenced evacuation of personnel on duty from Benisede, and three neighbouring flowstations (Opukushi, Ogbotobo and Tunu)."

The spokeswoman said that all four flow stations had been shut down following the explosion at the Trans Ramos pipeline on January 11.

"There is no new net impact on production as a result of this incident. Some 106,000 barrels per day of the SPDC joint-venture remains shut-in," she said.

She added: "A number of people have been given medical attention and about 10 persons are currently being hospitalised at the Shell hospital in Warri.There are reports of fatalities but we are only able to confirm one SPDC catering contractor staff fatality at this time. We cannot give further comments on reported non-SPDC cases and we are cooperating fully with the authorities."

She said that there were no current plans to permanently withdraw from the Delta region although it was not clear when workers would return.

"Following the general insecurity in the Benisede area, the company thought it prudent to minimise the risk to personnel by evacuating staff from the station and neighbouring fields."

The latest attacks have coincided with increased political tension across Nigeria as senior figures in Mr Obasanjo's People's Democratic Party jostle for position before national elections in 2007, their rivalry occasionally resulting in bloodshed.

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