Seven hostages are alive in Algeria, including three Belgians, two Americans, a Briton and a Japanese citizen, according to Islamist militants.
It is not known if the British hostage referred to is the captured 36-year-old Antrim man.
The information came from the Nouakchott Information Agency, which often carries reports from al-Qaida-linked extremist groups.
The militant spokesman said the kidnappers were attacked by Algerian helicopters as they tried to leave the complex.
Algeria’s news agency, citing local police, said four foreign hostages were freed in the operation.
The Algerian government would not immediately comment.
The Brigade claimed responsibility for the original attack on the Algerian gas plant.
The British Foreign Office said the Algerian authorities confirmed that an operation was underway at the gas plant deep in the desert at In Amenas where the hostages were being held.
Reuters reported a local source as saying that six hostages and eight of their captors were killed in an Algerian strike on the complex close to the Libyan border.
The militants contacted a news agency in neighbouring Mauritania earlier today to claim that 35 hostages and 15 militants died when Algerian helicopters began strafing the plant.
Amid conflicting reports, an Algerian official said earlier today that 20 people, including Europeans and Americans, had managed to escape the kidnappers.
Britain is allowing the Algerian government to take the lead in the crisis and has received no requests for support, Downing Street said today.