Western nations have warned of "bad news" from Algeria as confusion continued over an attempt to free foreign gas plant workers seized by Islamist militants. The numbers involved, killed and safe remain unknown.
An Algerian security forces' intervention at the sprawling In Amenas desert facility operated by Britain's BP, Norways Statoil and Algeria's Sonatrach continued into Friday.
Western governments have urged Algeria to safeguard surviving hostages' lives.
Algeria's state news agency APS said the forces had recaptured residential quarters Thursday, but production facilities were still held by militants, who claim that 35 hostages and 15 of their fighters were killed in Algerian airstrikes.
The APS news agency also reported on Friday that nearly 650 hostages had been freed, including 573 Algerians and more than half of the 132 foreign hostages.
The United States, France, Norway, Ireland and Japan have confirmed that their citizens had initially been among the hostages.
Reuters quoted an Irish engineer who survived as saying that he saw four jeeps full of hostages blown up by Algerian troops during the attempted intervention.
An Algerian security source had said two Japanese, two Britons and a French national were among at least seven foreigners killed, according to Reuters.
Algerian Information Minister Mohammed Said said the assault left "several people" killed or wounded. A "large number" of hostages had been freed.
"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," Said told APS.
Further 'bad news'
British Prime Minister David Cameron said: "We should be prepared for the possibility of further bad news."
"Already we know of one [Briton] who has died. It is a very dangerous, very uncertain, a very fluid situation," Cameron said.
A spokesman for Japan's new Prime Minister Shinzo Abe said he intended to break off a trip to Indonesia and had "conveyed his strong concern" to Algeria's government, urging it to "refrain from any action leading to the endangerment of people's lives."
Three Japanese workers of the Japanese engineering firm JGC Corp had been confirmed safe but 14 others remained unaccounted for, Chief Cabinet Secretary Yoshihide Suga added.
"We consider this Algerian army action to be regrettable," said Suga.
Norwegian Prime Minister Jens Stoltenberg said late Thursday that official information out of Algiers was confusing and incomplete.
No prior warning
Foreign governments said Algeria gave them no prior warning of Thursday's intervention. A senior US official said Washington had "strongly encouraged" Algerian authorities to make the hostages' safety their top priority.
Veteran Algerian Jihadist fighter Mokhtar Belmokhtar claimed responsibility for the initial hostage taking which began early Wednesday at In Amenas, a remote desert site in eastern Algeria.
The militants said they had mounted the raid on the gas facility in retaliation for the French military intervention against Islamist rebels in Mali, which borders Algeria from the southwest.
ipj/rc (dpa, AFP, Reuters)