Shell has withdrawn about 330 workers from four sites in the Niger Delta area of Nigeria following a gunboat attack.
Shell staff have started to leave the area
Gunmen fought Nigerian soldiers on Sunday as they overran the Benisede pumping station near the port of Warri.
One catering contractor died in the attack and ten Shell workers are being treated in a company hospital in Warri.
The evacuations from Benisede and three other pumping stations will not affect production, as it had been halted after a pipeline attack last Wednesday.
The latest attack helped to put upward pressure on oil prices, with markets already worried about the nuclear standoff involving Iran, the world's fourth-largest crude oil exporter.
In London the price for a barrel of Brent crude had risen by 71 cents to $62.97 after morning trading.
In two attacks last week, militants ruptured a major pipeline feeding an export terminal and kidnapped four foreign workers from another Shell oil rig in the region.
The hostages, who are still being held, come from the UK, the US, Honduras and Bulgaria, a Shell spokeswoman said.
Shell has 1,000 oil wells and around 80 pumping stations in the delta region.
But the firm said it had no current plans to pull any more of its workers out of the delta.
"The safety and security of our staff, contractors and the communities within which we operate is our main priority," Shell said.
Correspondents say the recent attacks will increase pressure on Nigeria's government to crack down on ethnic Ijaw militants who want more control over the region's oil revenues.
The Movement for the Emancipation of the Niger Delta, the group that says it is holding the hostages, has demanded the release of separatist leader Mujahid Dokubu Asari, who is being held on treason charges, and former Bayelsa State governor Diepreye Alamieyaseigha, who is accused of money-laundering.
"It must be clear that the Nigerian government cannot protect your workers or assets. Leave our land while you can or die in it," the group said in an e-mail statement. "Our aim is to totally destroy the capacity of the Nigerian government to export oil."
The kidnappings and explosion, the latest in a string of violent incidents in the troubled region, have slashed Shell's production there by some 220,000 barrels a day - almost 10% of Nigeria's average output of 2.6 million barrels.
In a statement about the latest attack, Shell said "heavily armed persons" attacked the platform early on Sunday.
"The attackers invaded the flow station in speedboats, burnt down two staff accommodation blocks, damaged the processing facilities and left," it added.
Last week gunmen attacked another platform kidnapping staff
Soldiers guarding the platform returned fire, Brigadier-General Elias Zamani, commander of a special task force assigned to the area, said.
According to the Reuters news agency, a number of soldiers and assailants also died in the latest attack.
Nigeria is Africa's leading oil exporter and the fifth-biggest source of US oil imports.