ROME (AP) _ The government summoned Israel's ambassador to the Foreign Ministry on Tuesday as it began its inquiry into the case of a former Israeli nuclear technician who says he was abducted from Rome to face spy charges.

A Rome prosecutor has begun investigating the claims of Mordechai Vanunu, 32, who has been charged with espionage related to the exposing of Israel's atomic secrets, Italian news agencies reported Tuesday evening.

Earlier Tuesday, Premier Bettino Craxi told a news conference he was not satisfied with Israel's explanations about the case.

The Foreign Ministry said it summoned Israeli Ambassador Mordechai Drory to impress upon him the necessity of a formal reply from his government on the case. The ministry quoted Drory as saying he had no information about the case and that he would relay the request to his government.

Vanunu is being held in custody until his trial, which will be held behind closed doors. No date has been set.

Vanunu is charged with aiding an enemy in wartime and two counts of aggravated espionage, defined as passing information with intent to harm. The wartime charge refers to the fact that Israel is in a technical state of war with all but one of its Arab neighbors.

Vanunu was employed as a technician for 10 years at Israel's Dimona nuclear facility about 85 miles from Tel Aviv. He was discharged last year.

Israel does not reveal any information about its nuclear capacity, saying only that it will not be the first nation to introduce nuclear weapons to the Middle East.

Vanunu disappeared in London on Sept. 30 after supplying a British newspaper with information and photographs purported to be of an Israeli nuclear weapons facility.

Israel said in November that he was being held incommunicado in jail in Israel but has not said how he ended up there.

Vanunu flashed a message written on his hand to reporters in Jerusalem on Sunday saying he was kidnapped in Rome on Sept. 30 after arriving on a British Airways flight from London.

The London Evening Standard reported on Monday that he was lured onto the flight by a female agent of the Mossad, Israel's secret services and was abducted by Mossad agents on arrival in Rome.

''We don't know yet whether the operation was carried out in Rome, even if there's reason to suspect (that it is true) because I don't understand why this man would lie,'' Craxi told reporters.

''We directly asked the Israeli authorities, who have been saying 'no comment,' '' the premier said.