Several Britons are still among Western hostages in a gas plant siege from Islamist gunmen.

William Hague earlier condemned the killing of a Briton at the plant near the border with Libya as “cold-blooded murder”.

One Briton and an Algerian were killed when around 20 attackers from an al Qaeda-backed group stormed the In Amenas facility, which is part-owned by BP.

They claimed to have seized 41 hostages, including several Britons, Americans and other Westerners, and remain in a stand off with Algerian forces who have surrounded the area.

Algerian state media reported that the Algerian workers have now managed to make it out of the compound.

Six people were wounded in Wednesday’s attack, which the group claims is retaliation for the French military intervention against al Qaeda-backed rebels in neighbouring Mali.

The raid is believed to have been planned by Mokhtar Belmokhtar, a one-eyed Islamist known as Mr Marlboro and The Uncatchable.

His group goes under various names including Khaled Abul Abbas Brigade, the Masked Ones and The Blood Battalion and is said to have links with al Qaeda in the Islamic Maghreb, a Mali-based militant group that wants to overthrow Algeria’s government.

Mr Hague said he was sceptical the raid was carried out retaliation for the offensive against Islamist fighters in Mali.

The Foreign Secretary said: “That is a convenient excuse, but usually operations like this take longer to plan.

“Whatever excuse is being used by terrorists and murderers, there is no excuse.”

Algerian interior minister Dahou Ould Kablia said his government would not negotiate with “terrorists”.

Sky’s Special Correspondent Alex Crawford, who is in Mali, said: “If negotiations are being ruled out and talks fail, then the only other option is some sort of rescue operation. It’s very tense all round.”

The plant has been surrounded by Algerian army and security forces, with army helicopters flying overhead. An Algerian security official has said the government is in talks with the US and France over whether an international force could help.

David Cameron is chairing an emergency meeting on the crisis this morning. A team has been sent from the Foreign Office to reinforce British embassy and consular staff in Algeria.

Mr Cameron “expressed his sympathy and support” when he spoke to Algerian prime minister Abdelmalek Sellal on Wednesday evening.

In its latest statement, BP said the situation remains “unresolved and fragile” and that a number of its staff are among the hostages.

The Irish government has said a 36-year-old Irish national was among the hostages. He was believed to be unharmed.

The Algerian interior ministry said the attack began when three vehicles carrying heavily armed militants ambushed a bus carrying employees from the gas plant to a nearby airport. They then targeted living quarters.

The militant group Katibat Moulathamine – The Masked Ones – has claimed responsibility.

A spokesman for the Katibat was reported as saying that Westerners of nine or 10 nationalities had been taken hostage, including seven Americans.

Five foreigners were being held in a factory, while 36 others were in living quarters at the plant, claimed the spokesman, who said the action was carried out in retaliation for Algeria allowing France to use its airspace to carry out raids on northern Mali.

Britain has provided two RAF C-17 transport aircraft to support the operation as well as offering to share intelligence with Paris.

[adrotate banner=”41″]