Algerian troops reportedly found the bodies of 25 hostages and captured five kidnappers at a remote gas plant after a bloodbath of captives that France called an "act of war" by Islamist militants.
Algeria's government -- the target of widespread foreign dismay last week at its decision to send in the army -- warned that the final death toll would likely be higher, but was only set to give an official figure later on Monday.
Governments scrambled to track down missing citizens as more details emerged after Saturday's final showdown between special forces and extremists who took hundreds hostage, demanding an end to French military intervention in Mali.
No official images of the attack have been released. But survivors took photos, seen by AFP, showing bodies riddled with bullets, some with their heads half blown away by the impact of the gunfire.
"They were brutally executed," said an Algerian who identified himself as Brahim, after escaping the ordeal, referring to Japanese victims gunned down by the hostage-takers.
A still image broadcast by Algeria's Ennahar TV on January 19, 2013 shows Islamist gunmen holding hostages after taking over a gas facility in Tiguentourine near In Amenas in the south of the country. Algerian troops reportedly found the bodies of 25 hostages and captured five kidnappers at the gas plant after a bloodbath of captives that France called an "act of war" by Islamist militants.
At least 23 foreigners and Algerians, mostly hostages, were confirmed killed after the militants seized control of the In Amenas gas plant deep in the Sahara desert on Wednesday.
Thirty-two kidnappers were also killed in the standoff, and the army freed 685 Algerian workers and 107 foreigners, the interior ministry said.
Ennahar television reported that another 25 bodies of hostages were found on Sunday as security forces combed through the sprawling complex run by Britain's BP, Norway's Statoil and Sonatrach of Algeria.
"Five terrorists were found still alive this morning (on Sunday)" at the plant, the private TV station added. But "three others are at large", station director Anis Rahmani told AFP.
"I fear that it (the toll) may be revised upward," Algerian Communications Minister Mohamed Said told a radio station, ahead of a news conference at 1330 GMT on Monday by Prime Minister Abdelmalek Sellal.
The one-eyed mastermind of the brazen hostage-taking, Mokhtar Belmokhtar, said in a video posted online that the attack was carried out by 40 fighters from the Muslim world and "European countries".
His Al-Qaeda-linked group "Signatories in Blood" threatened to stage attacks on nations involved in the French-led operation to evict Islamists from Algeria's neighbour Mali.
Map locating the Tigantourine gas plant, including provisional casualty toll. Algerian troops reportedly found the bodies of 25 hostages and captured five kidnappers at a remote gas plant after a bloodbath of captives that France called an "act of war" by Islamist militants.
French troops advanced Sunday towards Mali's Islamist-held north as Russia and Canada offered to help transport French and African soldiers to boost the offensive, and Germany also pledged assistance.
In a message published by the Mauritanian news agency ANI, Belmokhtar's group said it had tried to negotiate with the Algerian army to seek an "immediate end" to the intervention in Mali.
"But the Algerian army did not respond ... preferring to stage an attack which led to the elimination of the hostages."
French Defence Minister Jean-Yves Le Drian described the hostage-taking as an "act of war" because of the large number of people involved -- the biggest since the 2008 attack by Islamists extremists on the Indian city of Mumbai.
Most hostages were freed on Thursday in the first Algerian rescue operation, which was initially viewed by foreign governments as hasty, before the focus of anger turned on the jihadists.
"The blame for this tragedy rests with the terrorists who carried it out, and the United States condemns their actions in the strongest possible terms," President Barack Obama said, with one American confirmed dead.
Prime Minister David Cameron said six Britons and one British resident were thought to have been killed in the hostage crisis, which he said was a "stark reminder" of the threat of global terrorism.
Relatives of Kenneth Whiteside, 59, from Scotland, were "devastated" after hearing an Algerian co-worker describe seeing him being shot but dying bravely with a smile, Britain's Mail on Sunday reported.
Among the other hostages killed were at least one Algerian, one Colombian and two Romanians. Those still unaccounted for include several Japanese nationals, five Norwegians, two Americans and two Malaysians.
An Algerian employee of BP who identified himself as Abdelkader said he was at a security post on Wednesday with colleagues when he saw a jeep with seven people inside smash through the barrier and screech to a halt.
Getting out of the vehicle, one of the militants demanded their mobile phones and ordered them not to move, before disabling the security cameras.
"He said: 'You are Algerians and Muslims, you have nothing to fear. We're looking for Christians, who kill our brothers in Mali and Afghanistan and plunder our resources'."
Witnesses agreed that the hostage-takers were well informed about the In Amenas gas complex, close to the Libyan border, and suspected inside help.
They knew the internal procedures, the room numbers of the foreign workers, and they attacked the compounds of BP and Japanese services firm JGC, the only ones where there were foreigners, said a JGC employee called Riad.
But on a visit to the plant, Algerian Energy Minister Youcef Yousfi said it would be up and running within 48 hours, adding the damage was negligible and that security would be strengthened.