"Several" British nationals are caught up in a terrorist attack at a gas field in Algeria where workers have been taken hostage.
An Islamist militant group has claimed to have kidnapped up to 41 foreign nationals - including seven Americans and an Irishman in a dawn raid on the gas facility part-operated by BP, Sonatrach (the Algerian national oil company), and Statoil in Algeria.
Three people have reportedly been killed in the attack on the plant situated in the east of the country near the Libyan border.
Prime Minister David Cameron chaired a 45-minute meeting of the Government's crisis committee Cobra on the attack, attended by ministers from the Foreign Office and Ministry of Defence, as well as officials from other agencies.
His official spokesman said afterwards: "The ongoing incident has involved various nationalities, including several British nationals.
"We are working with BP to support the families of staff and provide consular assistance."
Mr Cameron is also expected to speak to Algerian Prime Minister Abdelmalek Sellal about the attack, later.
A Foreign Office spokeswoman said: "We can confirm that British nationals are caught up in a terrorist incident ongoing near the town of In Amenas at an oil installation near the Algerian border with Libya.
The In Amenas field (courtesy BP.com)"The British embassy in Algiers is liaising with local authorities."
The Foreign Office said it is working with BP to support the families of those involved.
BP is yet to confirm a link to reports that Islamist militants, said to be connected to al Qaeda, had seized a number of people in an attack that had a possible revenge motive for French military action in Mali.
It said in a statement that the site was "attacked and occupied by a group of unidentified armed people," and that some personnel are believed to be "held by the occupiers".
The company said it was seeking information as to whether any staff or contractors had been injured - and the identities and intentions of the people occupying the site.
It added it was contacting relatives of workers on the site.
A French citizen was killed, according to the AP news agency, which quoted an Algerian security official.
He suggested the attack on the base, about 60 miles from the Libyan border, came at 2am and the militants involved came from Mali.
The plant is situated in In Almenas, in eastern AlgeriaThe official claimed that the Algerian army had since surrounded the militants and their hostages and negotiations had started.
In its statement BP said: "We can confirm that there has been a security incident this morning at the In Amenas gas field in the eastern central region of Algeria.
"The In Amenas field is operated by a joint venture of which BP is a member. Algerian authorities are engaged with the incident; UK authorities have also been advised.
"BP has activated its emergency response system and is setting up a helpline for relatives."
The company did not say whether foreigners were taken away from the facility.
Ireland's Department of Foreign Affairs (DPA) confirmed a 36-year-old married man from Northern Ireland, travelling on an Irish passport, was among those taken.
It is understood that Japanese, Norwegian and French nationals were also part of the group.
Ireland's Deputy Prime Minister Eamon Gilmore called for the Irishman's immediate release.
He said: "The Government stands ready to use all the resources available to us to ensure that our citizen is released as soon as possible.
"I would ask that the family be allowed privacy at this difficult time."
The country's Department of Foreign Affairs added it was providing consular assistance to the family and was in close contact with its international partners and a wide range of other contacts in order to establish the facts of the situation.
A spokesman said: "At this stage, the identity and motives of the kidnappers is unknown."