David Cameron has warned that the West faces a decades-long struggle against Islamist terrorism in north Africa in the wake of the bloody and violent climax to the Algerian hostage crisis.
Amid warnings that the confirmed death toll of 23 hostages was set to rise, the Prime Minister said the militants who attacked the BP gas plant at In Amenas represented a "global threat" which required a "global response".
Mr Cameron disclosed three British nationals were now known to have died in the four-day stand-off, and three others were thought to be dead. A UK resident was also believed to have been killed.
Algerian bomb squads searching the remote desert complex for booby-trap devices left by the terrorists were said to have found 25 bodies.
Fears that the remaining militants had been about to blow-up the whole plant was one of the reasons given by the Algerian authorities for launching the "final assault", which ended the siege. By the time it was over, 32 of the terrorists who took part in the initial raid were dead, according to the Algerian interior ministry. It had been thought all the militants were killed, but there were reports that five had been captured alive.
The veteran jihadist Mokhtar Belmokhtar sent a video to a Mauritanian-based news website in which he claimed one of his cells, known as "Those Who Sign In Blood", was responsible for the attack.
Foreign Secretary William Hague branded the militants "cold-blooded murderers" and said reports they had "executed" seven of their hostages before the final battle could well be true. He said: "That sort of thing is quite likely to have happened."
Mr Cameron, who monitored the final stages of the crisis from Chequers, said the attack was a "stark reminder" of the continuing threat from international terrorism. Looking pale and tired, he vowed to use Britain's chairmanship of the G8 to ensure the issue was right at the top of the international agenda.
He said: "This is a global threat and it will require a global response. It will require a response that is about years, even decades, rather than months. It requires a response that is patient and painstaking, that is tough but also intelligent, but above all has an absolutely iron resolve, and that is what we will deliver over these coming years."
BP later said four of its employees from the joint venture gas plant were missing. It said:: "At the time of the attack there were 18 BP employees at In Amenas; 14 of them are safe and secure. Two of the 14 have sustained injuries, but these are not life-threatening. BP remains gravely concerned about four of its employees who are missing. There is no further confirmed information regarding their status at this time."