Algerian militants are claiming that as many as 34 hostages, including at least six foreigners, and 15 of their kidnappers were killed on Thursday in a helicopter attack undertaken by the Algerian military as the hostages were being moved to another location. A day earlier, 41 foreigners — including Norwegian, Japanese, British and American citizens — and more than 100 Algerians had been kidnapped at a natural gas complex in the southern part of the country. Sources in the British government describe the 34 figure as "high." According to the Algerian military, the operation is "ongoing."

Update: The report that the hostages were killed appears to have initially come from ANI, which interviewed one of the kidnappers. CBS says a diplomatic source has confirmed "casualties among both terrorists and hostages."

The "Masked Brigade," the group claiming responsibility for taking the hostages, described the operation yesterday as retaliation for the Algerian government allowing France use of its airspace in the country's attacks on extremist Malian rebels. Led by veteran fighter Mokhtar Belmokhtar, pictured above, and numbering about 20, the group had been demanding safe passage with their prisoners out of the natural gas facility, which had been surrounded by the Algerian military.

Update: A kidnapper tells Mauritian news outlet ANI that seven foreign hostages are still being held, alive, by the militants: two Americans, three Belgians, one Japanese citizen and one British citizen. Since seven Americans were said to have been taken hostage, this could mean that five American citizens were killed in the Algerian government's attack; on the other hand, a source has told Reuters that only six foreign hostages were killed, and previous reports held that some Americans had escaped with a group of hostages. (Reuters, speaking to local residents and sources, has also reported that as many as 180 Algerian hostages escaped.)

According to the Algerian APS news agency, four foreign hostages (one French citizen, two Scots and a Kenyan) have been freed by the Algerian army, though no other details have been provided. BBC News security correspondent Frank Gardner reports the following:

A UK Government official has confirmed to me that a "proactive Algerian military operation to free the hostages is under way". They cannot confirm if there is any truth in militant claims of a helicopter strike killing kidnappers and captives in a bus.

BP is withdrawing non-essential workers from Algeria, says CNBC. They have since released a press release, which you can read here.