PGS, which provides seismic data for oil and gas companies, said the two were kidnapped in the very early hours of on Thursday morning. The British Foreign Office also confirmed the incident.
"They were abducted by a group of armed men from the vessel HD Commander while it was anchored near the Funiwa platform, off the coast of Bayelsa State," the company said in a statement.
PGS told a news conference in Oslo it had not received any demands from the kidnappers and did not know who they might be. It said the men's families had been informed of the abductions.
The firm said its other crew members were uninjured but said it was nonetheless taking measures to ensure their safety.
This is the second kidnapping affecting the company. A similar incident took place on June 20, when two Filippino workers, Joseph Doctolero and Pacifico Gajo, were kidnapped by six armed men near Port Harcourt, the hub of the Niger Delta oil industry.
The men were contract employees for a firm called Beaufort International and were abducted from a vessel manoeuvring in a channel of the Delta. They were released on June 25.
The Foreign Office in London also confirmed that two men had been taken hostage in the early hours of on Thursday morning, around 15 miles off the coast. "We can confirm that a British man and an American have been taken hostage," a spokeswoman said. "We are in contact with the High Commission in Nigeria, the Nigerian authorities and the men's employers," she said.
No-one has claimed responsibility so far for the seizure of the two oil workers.
The Movement for the Emancipation of Niger Delta (MEND), which has claimed responsibility for several abductions of foreign oil workers in the past, told AFP on Thursday it was not involved in the latest kidnapping.
"It is a community-related dispute and (has) nothing to do with us," MEND spokesman Jomo Gbomo told AFP in an email.
"They are being held in a community over a dispute concerning (US oil firm) Chevron. I am certain they will soon be released," the short message said.
The US embassy in Nigeria said it was seeking details of the abduction.
"We are aware that an American has been kidnapped but we are yet to get the details," an embassy official who declined to be named told AFP.
The Niger Delta is the hub of Nigeria's multi-billion-dollar oil industry.
Since January separatists seeking a larger share of the oil wealth for the Delta's 14-million strong ethnic Ijaw community have been blamed for a spate of violent attacks on multinational oil firms and their personnel.
Some 60 Nigerian security workers have been killed by suspected militants during attacks on oil facilities in the restive Delta. Dozens of local and expatriate workers have been kidnapped and held for days or weeks before being released unharmed.
President Olusegun Obasanjo called, during a visit to the volatile region last month, for an end to attacks on foreign oil workers and the destruction of oil facilities. He said they gave the nation a bad image.
Last week, seven expatriates working for sub-contractors to US oil group ExxonMobil were freed after more than two weeks in captivity.
The seven -- four Britons, a Romanian, a Malaysian and an Indonesian working for Sparrow Offshore and Oceaneering International were kidnapped by unknown armed men who attacked an installation in Eket, a major town in south-eastern Akwa Ibom State.
Two Nigerian employees were believed to have been killed during the attack, for which no-one has yet claimed responsibility.
Nigeria is Africa's largest oil producer and the world's sixth largest exporter of crude. It derives more than 95 percent of its foreign exchange earnings from oil and gas but unrest in the Niger Delta has cut output by around one quarter.
Copyright AFP (Agence France-Presse), 2006
