Islamist militants attacked a gas production field in southern Algeria on Wednesday, kidnapping at least seven foreigners and killing a French national, local and company officials said.
An al Qaeda-linked group operating in the Sahara said it had carried out the raid on the In Amenas facility, Mauritania's ANI news agency reported.
The field, located close to the border with Libya, is operated by a joint venture including BP, Norwegian oil firm Statoil and Algerian state company Sonatrach.
Five Japanese nationals working for the Japanese engineering firm JCG Corp were kidnapped as well as a French national, local officials said. An Irishman was also seized, the Irish government said.
A French national was killed in the attack, a local source said, but it was unclear if the victim was the same person who had been kidnapped.
The foreigners were taken from In Amenas in the morning. Algerian troops had mounted an operation to rescue the hostages and had also surrounded the workers' camp at Tiguentourine, a local source said.
Algeria has allowed France to use its air space during its military intervention against Al Qaeda-linked Islamist rebels in Mali, although officials have yet to make a link between Wednesday's attack and the conflict in Algeria's southern neighbor.
ANI, which has regular direct contact with Islamists, said that fighters under the command of Mokhtar Belmokhtar were holding the foreigners seized from the gas field.
Belmokhtar for years commanded al Qaeda fighters in the Sahara before setting up his own armed Islamist group late last year after an apparent fallout with other militant leaders.
BP confirmed there had been a "security incident" at the In Amenas field but could give no more details.
Statoil, a minority shareholder in the venture, said it was notified of the incident on Wednesday morning but could not say if any of its fewer than 20 employees were affected.
Statoil described the incident as serious and called it an emergency situation.
BP said the field was approximately 1,300 km (825 miles) from the capital, Algiers.
The five Japanese work for the engineering firm JGC Corporation, Jiji news agency reported, quoting company officials. JGC has a deal with Sonatrach-BP-Statoil Association for work in gas production at In Amenas.
In Tokyo, the Japanese Foreign Ministry said it was gathering information on the situation but could not comment. French Foreign Ministry officials also said they had no immediate comment and were trying to verify the reports.