NOUAKCHOTT  - Gunmen in Algeria who are holding about 60 hostages at a gas plant, want to swap the American hostages for prisoners held in the United States including Pakistani Aafia Siddiqui, the ANI news agency quoted sources close to their leader as saying on Friday.The abductors, who are also holding other Algerian and foreign hostages, have also demanded negotiations for an end to French intervention in Mali, the agency said, quoting sources close to Mohktar Belmokhtar.Veteran fighter Belmokhtar, a one-eyed Algerian militant apparently with ties to al Qaeda, has claimed responsibility for launching Wednesday’s attack.ANI said Belmokhtar, in a video that would be distributed to the media, proposed proposed that “France and Algeria negotiate an end to the war being waged by France in Azawad” (northern Mali).He also proposed “exchanging American hostages held by his group (the ‘Signatories in Blood’)” for Egyptian Omar Abdul Rahman and Pakistani Aafia Siddiqui, who are jailed in the United States on charges of terrorist links.Abdul Rahman, the spiritual leader of the Jamaa Islamiya group, was convicted in 1995 for his role in a 1993 attack on the World Trade Centre in New York City, in which six people were killed.He is serving a life sentence for the attack in which hundreds more people were injured when a truck bomb was detonated in the building’s garage.Abdul Rahman, known as the “blind sheikh,” was also convicted of plotting to bomb other New York targets including the United Nations and a plan to assassinate ousted Egyptian president Hosni Mubarak.Mubarak’s successor, Islamist President Mohamed Morsi, said earlier this month he will urge US President Barack Obama to free Abdul Rahman, during a visit he is due to make to the United States later before the end of March.Siddiqui, a US-educated neuroscientist, is an al Qaeda-linked would-be extremist who tried to murder American officers on July 18, 2008, after she was detained by security services in Afghanistan. The abductors are believed to have at least four American nationals in their custody.There were over 710 people working on the plant when it came under attack from militants. However, action by Algerian special forces managed to free 650 of those including 573 Algerians and 100 of the 132 foreigners who work at the plant. The fate of the rest was unknown, but militants claim they still have hostages.British Prime Minister David Cameron Friday warned that the In Amenas plant was a "large and complex site and they are still pursuing terrorists and possibly some of the hostages in other areas of the site."Some of those who escaped or spoke of their ordeals said they had had explosives wrapped around their necks. Others said they hid, petrified, under beds, in gaps above ceilings or wherever they could.Cameron, who said he was "disappointed" not to have been told by the Algerians in advance, said "significantly" fewer than 30 British citizens remained at risk at the field, operated jointly by Britain's BP, Norway's Statoil and Sonatrach of Algeria.BP said a "small number" of its staff was unaccounted for on Friday, adding that it had evacuated hundreds of workers from the complex and other fields.US Defence Secretary Leon Panetta said in London US officials were "working around the clock" to secure the safe return of an unknown number of American hostages."Terrorists should be on notice that they will find no sanctuary, no refuge. Not in Algeria, not in north Africa, not anywhere," he said.A senior US official said Washington "strongly encouraged" the Algerian authorities to make the hostages' safety their top priority.Japanese plant builder JGC said it had now accounted for 17 of its employees, but that the whereabouts of 61 more remained unknown.Statoil said another of its Norwegian employees was now safe, but that the fate of eight others was unknown.France said two of its nationals had returned safely but it had no word on two others reportedly seized. Vienna said one Austrian had been released.One man from Northern Ireland, Stephen McFaul, escaped. His brother said he fled when the convoy he was in came under army fire. He had earlier "had explosives tied around his neck."Alexandre Berceaux, who works for France's CSI Catering, said he stayed in his room and hid before finally being freed by Algerian troops on Thursday evening."I was under the bed and I put boards everywhere just in case," Berceaux said. "I had a bit of food, a bit to drink. I didn't know how long it would last."The gunmen from a group known as "Signatories in Blood" want to negotiate an end to French intervention in Mali and exchange American hostages for prisoners held in the United States, Mauritanian news agency ANI quoted sources close to their leader, Mokhtar Belmokhtar, as saying on Friday.ANI reported that Belmokhtar, a veteran Algerian Islamist with Al-Qaeda ties who has claimed responsibility for Wednesday's attack, had proposed that Paris and Algiers negotiate "an end to the war being waged by France in Azawad" (northern Mali).In what ANI said was a video that would be released to media, he also proposes exchanging American hostages held by his group for Egyptian Omar Abdul Rahman and Pakistani Aafiah Siddiqui, jailed in the United States on charges of terrorist links.Algeria has insisted it will not negotiate with "terrorists."Earlier, a spokesman for the group said that, "taking into account the suffering of the Algerian people, we promise the regime in place that there will be more operations," ANI said.The hostage drama dragged Algiers and Western powers into the Mali conflict, taking the spotlight off French and government troops battling Islamists who control the country's vast desert north.The Malian army has retaken the centre of Konna, which had fallen to Islamists advancing from the north and sparked French military intervention, the military and a regional security source said on Friday.On Thursday, more French troops poured into Mali, boosting their number to 1,400, Paris said. At full strength the force will reach 2,500 soldiers.French Foreign Minister Laurent Fabius said he would attend an emergency summit of west African states on Saturday to help accelerate the deployment of a regional military force.