TUNIS, JAN. 15 (TUESDAY) -- A turncoat bodyguard assassinated two senior deputies of PLO leader Yasser Arafat Monday night at a house outside Tunis, Palestinian officials said. A third man, a member of their security team, was also killed.

The gunman held two relatives of one of the victims hostage for six hours before being arrested.

A senior Palestinian commander in Tunis said the killer is a former member of Abu Nidal's terrorist PLO faction, sworn enemies of Arafat since 1973. But "we still don't know who he's working for," the commander said. "He may also be working for the Israelis."

The assassin, armed with an AK-47 assault rifle, took the hostages after killing Salah Khalaf, better known as Abu Iyad who was Arafat's second-in-command and counterintelligence chief; Hayel Abdel-Hamid, the PLO's security chief; and Abu Mohammed Omari, Khalaf's aide, sources here said.

Six hours later, PLO guerrillas and Tunisian police stormed into Abdel-Hamid's house in the suburb of Marsa, arrested the assailant and freed the two women hostages -- Abdel-Hamid's wife and daughter -- unharmed, the commander said.

The death of Khalaf left Arafat as the sole survivor among the three original founders of Fatah, the first PLO group and its largest faction.

Khalaf, is said to have been the mastermind of the murders of 11 Israeli athletes at the Munich Olympics in 1972. He had cultivated a moderate position in recent years.

Abdel-Hamid's nom-de-guerre was Abul Hol. Both men were in their late 50s.

At the United Nations, the PLO's representative blamed Israeli agents for the killings, which he compared to the April 16, 1988, assassination of the other PLO founder, Khalil Wazir. That killing also took place in Tunisia.

"It doesn't take a genius" to figure out who killed the two leaders, said the representative, M. Nasser Kidwa.

The gunman was identified only as Hamza, Abdel-Hamid's bodyguard, by the commander, who was interviewed by telephone from Nicosia, Cyprus.

Arafat was on his way from Amman to Paris for talks on the gulf crisis when the shooting occurred, but canceled his trip, Daniel Bernard, a French Foreign Ministry spokesman, said in Paris.

The Palestinian commander said Hamza long has had ties to the Libyan-backed Palestinian terrorist Abu Nidal but quit the group and began working as Abdel-Hamid's bodyguard six months ago. "He may still have ties to Abu Nidal, but he may also be working for the Israelis," said the commander, who spoke on condition of anonymity.

There has never been an official claim of responsibility for Wazir's 1988 slaying. Israeli sources said the Mossad intelligence service and the Israeli navy killed Wazir because he helped organize Palestinian rioting on the West Bank and Gaza Strip.

The commander said Monday night's attack began when Hamza grabbed Abdel-Hamid's wife and daughter. He held them at gunpoint as he stormed into the room where the PLO officials were meeting and opened fire, he said.

Through a window, he shouted at bewildered Tunisian and PLO security men outside the house that he would kill the hostages unless he was given safe passage to the airport and a plane to fly him out. He did not say where he wanted to go, the commander added.