The first pictures to emerge from an Algerian gas complex stormed by Islamist militants show gun-toting kidnappers in camouflage, with their faces covered, guarding hostages at the desert site.

The daytime photos were obtained by Japan's Kyodo news agency, which told AFP that they were taken by an unidentified Algerian worker at the vast complex before the crisis ended in a bloodbath with at least 37 foreign workers dead.

The mobile-phone pictures were taken on January 16, the first day of the siege, Kyodo said, citing the pictures' metadata.

In one photo, a militant is shown with brown cloth around his head and face, leaving a small eye slit, and wearing black gloves. He is carrying what appears to be an AK-47 assault rifle, and stands among casually dressed workers.

Hostages, said by Kyodo to be Algerian, are shown standing or sitting on the dusty ground with packed travel bags and plastic water bottles around them. They are wearing jackets and woolly hats. None of their faces can be seen clearly.

The photo, which Kyodo said was taken outside a workers' residence, also showed white sport utility vehicles behind a security fence in the distance.

Another picture shows three armed and camouflaged kidnappers guarding foreign workers sitting against a tan-coloured, one-storey structure with small windows. Small trees and street-lamps surround the building.

Other armed Islamists are shown bending over to check unidentified items on a paved path near the building while a group of workers, identified as Algerian, look on.

A third photograph shows Algerian workers standing near a worker residence, also surrounded by packed travel bags. An unidentified man in the centre of the photograph, possibly a worker, is shown wearing a blue jumpsuit while a man carrying a rifle is pictured from behind.

The fate of those pictured is unknown.

Japanese media have given blanket coverage to the crisis and its aftermath as the country reels from its biggest death toll in an act of terror since the September 11 attacks of 2001.

At least seven Japanese nationals were killed in the Algeria attack, and the government is unable to account for three others.