The four foreign oil workers kidnapped by Nigerian militants have told Reuters news agency they are in good health.
The four – from the UK, US, Bulgaria and Honduras – were taken hostage by armed men on speedboats a week ago while in the Niger Delta region.
There was a further gunboat attack on a pumping station over the weekend, prompting oil giant Royal Dutch Shell to withdraw some 330 workers.
The instability has led to a 10% fall in Nigeria’s oil production.
“I’d like y’all to contact my family and let them know that I’m alright, these people are treating me good, but the climate is not what it should be,” a man identifying himself as US citizen Patrick Landry told Reuters by telephone.
A man who said he was Briton Nigel Watson-Clark said that the Nigerian military should not try to use force to rescue them.
He also read out five demands, which the kidnappers said should be met within 48 hours:
Local control of the region’s oil wealth
The payment of $1.5bn by Shell to Bayelsa State to compensate for pollution
The release of separatist leader Mujahid Dokubu Asari, being held on treason charges
The release of former Bayelsa State governor Diepreye Alamieyaseigha, accused of corruption and money-laundering
The release of another ethnic Ijaw militant.
Brigadier-General Elias Zamani, who heads a military task force in the area told Reuters he had not yet located the hostages.
He also said that four soldiers and eight assailants had died on Sunday, as gunmen overran the Benisede pumping station near the port of Warri.
“The safety and security of our staff, contractors and the communities within which we operate is our main priority,” Shell said.
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.
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.
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 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.