ALGIERS, DEC. 29 -- Hijackers thought to be Islamic fundamentalists were holding more than 50 hostages tonight after commandeering an Algerian passenger jet, officials said. Sources said the hijackers demanded fuel to fly to another country.

The Air Algerie jetliner was carrying 88 people, including six crew members, when it was hijacked Friday night on a domestic flight from the Saharan resort of Ghardaia to the capital, Algiers. The Boeing 737 was forced to land in the eastern city of Annaba, where the hijackers today released 31 of the passengers.

{Five more people were released shortly after midnight Sunday, Reuter reported, leaving 46 passengers and six crew members in captivity.}

There were conflicting reports about the hijackers' identities. Transport Minister Hassan Kahlouche said two Algerian males were responsible for the crime. He said they had made no political statements or demands. "Right now, this only concerns a simple affair of common law," he said.

However, an Algerian official close to negotiations with the hijackers said they probably are Algerian Moslem fundamentalists protesting a crackdown against an allied fundamentalist movement in Tunisia. Algerian radio cited police sources as saying they are Tunisian fundamentalists.

In an interview with Algerian radio, an unidentified freed hostage described the hijackers as "delinquents" about 25 years old. She said at least one of the hijackers was armed with a medium-caliber, semiautomatic pistol.

Kahlouche said there had been no violence so far. Another Algerian official, speaking on condition of anonymity, quoted freed passengers as saying the hijackers "showed no physical or verbal violent intentions" and made no statements about their motives.

The state-owned Air Algerie said in a communique that the passengers were in good condition, but gave no details.

The airline said there were 14 foreign nationals among the passengers. In Washington, the State Department said no Americans were aboard. Kahlouche said the foreigners on board included French, German, Italian and Japanese citizens.

Algerian Interior Minister Mohammed Salah Mohammedi negotiated throughout the day with the hijackers. Security forces surrounded the aircraft, but other scheduled flights took off and landed throughout the day.

Late today, Mohammedi said the hijackers would not be allowed to leave Annaba and suggested they were wearing down. "They're tired," Mohammedi said. "It's necessary to know how to profit from it."

Sources close to the negotiations said the hijackers hoped to fly to Egypt. But a presidential palace spokesman in Cairo, speaking anonymously, said, "We gave instructions to all airports not to receive terrorists."

Egypt's Middle East News Agency quoted the French-language Radio Monte Carlo as saying the hijackers wanted to go to Libya. No source was cited.

Algerian sources said the hijackers demanded water and enough fuel to fly to a foreign country from Annaba, which is about 250 miles east of Algiers, on the Mediterranean coast near the Tunisian frontier.

Algerian officials confirmed that a total of 31 passengers had been freed but did not disclose their nationalities nor the number of hijackers. Witnesses said the hostages were freed in groups over a period of hours and said many of those freed were children or appeared to be foreigners.

The hijackers, who seized the aircraft shortly after takeoff Friday evening, first demanded to fly to Carthage in Tunisia, Algerian police sources said, but were refused permission to land. The pilot was forced to land instead at Annaba, touching down after midnight.