A number of foreign nationals taken hostage by armed militants in Algeria have escaped, it is being reported.

One Briton has been killed and others are feared dead among those held by an Islamist group at an Algerian gas field complex.

An Algerian official said 20 people, including Europeans and Americans, had got away. The militant group has claimed it is holding 41 foreigners in the complex. The Foreign Office was unable to confirm that any hostages had escaped.

Britain is allowing the Algerian government to take the lead in the crisis and has received no requests for support, Downing Street said.

One hostage, identified as a Briton, told Al Jazeera: "We are receiving care and good treatment from the kidnappers. The (Algerian) army did not withdraw and they are firing at the camp." He urged negotiation to "spare any loss of life". Another hostage who spoke to France 24 television said they were being forced to wear explosive belts and the heavily armed gunmen were threatening to blow up the base if the Algerian army stormed it.

A number of Scots are among those being held, Scotland's First Minister Alex Salmond told MSPs. Prime Minister David Cameron's spokesman said the situation was "very serious and dangerous" but the Government was "working through" the Algerians and BP, which part-controls the facility that was stormed. "Our focus is on working through the Algerian government and the company," the Downing Street spokesman said.

Oil giant BP, which part-controls the facility that was attacked, said armed groups were still on-site holding a number of its staff, and described the situation as "unresolved and fragile".

The terrorist group claimed it targeted the Westerners, including seven Americans, in retaliation for the French military intervention against al Qaida-backed rebels in neighbouring Mali.

The family of a 36-year-old married Irishman, from west Belfast, who has been taken hostage have appealed for his release. In a statement read by Sinn Fein MP Paul Maskey, they said they have not heard from him since the compound was attacked. They said: "We are all very concerned about his welfare and want to see him released to us as a matter of urgency, free from harm. Our thoughts are with him and all the other captives."

A second meeting of the Government's emergency response committee Cobra was held this morning and another will be convened this afternoon.