As Algerian TV reported that the bodies of 25 more hostages had been discovered inside the gas plant on Sunday, workers’ families were still awaiting for news about their loved ones.
UK energy giant BP had 18 staff at the complex when the raid by Islamist rebels began on Wednesday.
“Tragically we now know that three British nationals have been killed and a further three are believed to be dead, and also a further British resident is also believed to be dead,” said British Prime Minister David Cameron.
Workers from a dozen countries were on site at the time the crisis began including Norway and Japan.
Oslo says five people are still unaccounted for, while Japan has yet to confirm the whereabouts of 10 of its 78 workers.
Japanese Prime Minister Shinzo Abe said: “From what we’ve heard from the Algerian government, there is indeed grim information about our citizens.”
Tokyo was particularly frustrated at the lack of communication from Algerian authorities during the siege.