At least 22 foreign hostages remained unaccounted for on Friday after Algerian forces stormed a desert gas complex to free hundreds of captives taken by Islamist gunmen.
A further 30 hostages, including several Westerners, were killed in the assault along with at least 11 of their captors, an Algerian security source told Reuters.
Western leaders whose compatriots were being held did little to disguise their irritation at being kept in the dark by Algeria before the raid - and over its bloody outcome. French, British and Japanese staff were among the dead, the source said.
An Irish engineer who survived said he saw four jeeps full of hostages blown up by Algerian troops whose commanders said they moved in about 30 hours after the siege began because the gunmen had demanded to be allowed to take their captives abroad.
The crisis posed a serious dilemma for Paris and its allies as French troops attacked the hostage-takers' al Qaeda allies in neighbouring Mali. It also left question marks over the ability of OPEC-member Algeria to protect vital energy resources and strained its relations with Western powers.
Two Japanese, two Britons and a French national were among at least seven foreigners killed, the source told Reuters. Eight dead hostages were Algerian. The nationalities of the rest, as well as of perhaps dozens more who escaped, were unclear. Some 600 local Algerian workers, less well guarded, survived.
Fourteen Japanese were among those still unaccounted for by the early hours of Friday, their Japanese employer said, while Norwegian state energy company Statoil, which runs the Tigantourine gas field with Britain's BP and Algeria's national oil company, said eight Norwegian employees were still missing.
A diplomatic source said Britain had not received any information to suggest the hostage situation had ended.
"The situation is still really fluid on the ground. We have no information from the Algerian authorities that it's over," the source said.
Japan's Prime Minister Shinzo Abe has cancelled part of his trip in Southeast Asia, his first overseas trip since taking office, and is considering flying home early due to the hostage crisis, Japan's top government spokesman said on Friday.
"The action of Algerian forces was regrettable," said Japan's Chief Cabinet Secretary Yoshihide Suga, adding Tokyo had not been informed of the operation in advance.
Americans, Norwegians, Romanians and an Austrian have also been mentioned by their governments as having been captured by the militants who called themselves the "Battalion of Blood" and had demanded France end its week-old offensive in Mali.
Underlining the view of African and Western leaders that they face a multinational Islamist insurgency across the Sahara - a conflict that prompted France to send hundreds of troops to Mali last week - the official source said only two of the 11 dead militants were Algerian, including the squad's leader.
The bodies of three Egyptians, two Tunisians, two Libyans, a Malian and a Frenchman - all assumed to have been hostage-takers, were found, the security source said.
The group had claimed to have dozens of guerrillas on site and it was unclear whether any militants had managed to escape.
The overall commander, Algerian officials said, was Mokhtar Belmokhtar, a veteran of Afghanistan in the 1980s and Algeria's bloody civil war of the 1990s. He appears not to have been present and has now risen in stature among a host of Saharan Islamists, flush with arms and fighters from chaotic Libya, whom Western powers fear could spread violence far beyond the desert.
"NO TO BLACKMAIL"
Algeria's government spokesman made clear the leadership in Algiers remains implacably at odds with Islamist guerrillas who remain at large in the south years after the civil war in which some 200,000 people died. Communication Minister Mohamed Said repeated their refusal ever to negotiate with hostage-takers.
"We say that in the face of terrorism, yesterday as today as tomorrow, there will be no negotiation, no blackmail, no respite in the struggle against terrorism," he told APS news agency.
British Prime Minister David Cameron, who warned people to prepare for bad news and who cancelled a major policy speech on Friday to deal with the situation, said through a spokesman that he would have liked Algeria to have consulted before the raid.
A Briton and an Algerian had also been killed on Wednesday.
U.S. officials had no clear information on the fate of Americans, though a U.S. military drone had flown over the area. Washington, like its European allies, has endorsed France's move to protect the Malian capital by mounting air strikes last week and now sending 1,400 ground troops to attack Islamist rebels.
A U.S. official said on Thursday it would provide transport aircraft to help France with a mission whose vital importance, President Francois Hollande said, was demonstrated by the attack in Algeria. Some fear, however, that going on the offensive in the remote region could provoke more bloodshed closer to home.
The apparent ease with which the fighters swooped in from the dunes to take control of an important energy facility, which produces some 10 percent of the natural gas on which Algeria depends for its export income, has raised questions, over the value of security measures that are outwardly draconian.
(Additional reporting by Ali Abdelatti in Cairo, Eamonn Mallie in Belfast, Gwladys Fouche in Oslo, Mohammed Abbas in London and Padraic Halpin and Conor Humprhies in Dublin; writing by Alastair Macdonald; editing by Peter Millership and Michael Perry)