Islamists have stepped up retaliation against French military intervention in Mali by abducting six BP workers, five Japanese and one Irishman, and killing their French colleague at an oil facility in southern Algeria.

French-language newspaper in Algeria El Watan reported that two British security guards were also killed in the attack. The Foreign Office said it "was seeking clarification from oil companies working in the area as to whether they have personnel involved".

The hostages were seized from the plant in the region of In Amenas, 60 miles (100km) from the Libyan border, and Algerian troops have been drafted in to launch a rescue bid, according to Reuters.

Oil giant BP confirmed there had been a "security incident" at its facility but did not give further details. It has set up a helpline for relatives.

The abduction of the Irish worker brought a swift response from Ireland's Tánaiste and Minister for Foreign Affairs and Trade, Mr. Eamon Gilmore, T.D., who called for his immediate release.

The Consular Assistance unit within the Department is supporting the hostage's family, and is in close contact with its international partners and a wide range of other contacts in order to establish the facts of the situation.

"The Government stands ready to use all the resources available to us to ensure that our citizen is released as soon as possible," the Tánaiste said today, adding that "I would ask that the family be allowed privacy at this difficult time."

The five Japanese workers were employed by engineering firm JGC Corporation, which was contracted to Sonatrach-BP-Statoil Association for work in gas production at In Amenas.

A Western diplomat had earlier said that British and Norwegian staff had been seized, but there were no further details.

At this stage, the identity and motives of the kidnappers is unknown.

Algeria has allowed France to go though its airspace to conduct air raids against Islamist rebels in Mali.