A Briton is among four foreign oil workers kidnapped in Nigeria, it has been confirmed.
The men were seized from Shell's Trident 8 oil rig in the Delta region
The men, who were sub-contractors working for oil giant Royal Dutch Shell, were seized by gunmen from an offshore oil rig in the Delta region.
An Irish citizen is also feared to have been kidnapped in a separate incident.
A Foreign Office spokeswoman said no further information was being released as it did not want to jeopardise the safety of the kidnapped men.
The hostages come from the UK, the US, Honduras and Bulgaria, a Shell spokeswoman said.
Eco-drill, the Aberdeen-based firm through which the Briton was contracted, said in statement: "Emergency response procedures have been instigated by Shell and they are working in country to resolve the situation."
The Irish Department of Foreign Affairs has confirmed it is providing consular assistance to the family of an Irishman who contacted its officials on Thursday.
"Our embassy in Abuja is trying to establish what the situation is," said a spokesman.
Elsewhere in the Delta, a major pipeline that feeds an export terminal has been ruptured by militants, forcing production to lose about 106,000 barrels a day.
Meanwhile, the first audit of Nigeria's oil and gas industry has been published and, without finding direct evidence of fraud, it reveals "accounting weaknesses".
Discrepancies worth hundreds of millions of dollars were found between what oil companies paid in taxes and what the government said it received.
Kidnappings and pipeline explosions are common in the Niger Delta region, where local groups complain they do not see the benefits of the area's oil wealth.
Shell says it is evacuating oil workers from the offshore facility where the kidnapping took place.
Ransom demands are often made in similar cases and the hostages are usually released unharmed.