Under the dimming light of the hot Sunday sun and using advanced electronic technology to pinpoint their targets, Israeli warplanes dropped several tons of bombs on the Osirak nuclear reactor near Baghdad and in two minutes left it a pile of rubble.

The raid, which Israel announced Monday, took the Israeli crews over more than 1,000 miles of Arab air space to their target while apparently avoiding any major interference. Although details of the mission were still scarce yesterday, the flight apparently involved months of preparation and tests, subterfuge as the pilots apparently used Arabic to communicate to avoid alerting their enemies and thorough briefing on details of the French-built nuclear complex outside Baghdad.

Israeli Air Force Lt. Gen. David Ivri, in a press conference in Jerusalem yesterday, said the mission was carried out with such precision that the debriefing of the pilots was "rather boring."

The Israeli operation appears to indicate an extraordinarily detailed knowledge of the layout of the $260 million Baghdad nuclear complex that was about to be completed after more than five years of planning and construction. The bombs hit only the 70-megawatt reactor, which was not on line yet, and missed the smaller, 1-megawatt research facility in the complex. At the press conference in Jerusalem yesterday, the Israeli chief of staff, Lt. Gen. Rafael Eitan, said the damage to the main reactor seemed to be complete, but that Israel had no evidence of damage to the core.

U.S. intelligence sources as well as sources to the nuclear industry and regulatory bodies here said, however, that the Israelis had not destroyed the $100 million plant, but had severly damaged its concrete shell, which was knocked completely off its foundation and onto its side. They estimated the damage at $25 to $30 million.

The more valuable reactor and the pumps, valves and electronic machinery inside the plant suffered little damage, these sources said. It would take about 18 months to rebuild the entire plant and replace the parts, they estimated.

To further complicate the issue, however, some of the 150 French technicians, who were ordered back to Paris following the raid, said that the reactor had been made unuseable.

Details of the mission slowly surfaced yesterday in Washington, Paris and Jerusalem. But the Israelis, citing national security interests, refused to comment on much of the raid.

Ivri said the Air Force had been preparing for the raid for months and had constructed models of the target and tested different types of aircraft for effectiveness. But the very few officials who knew about the topsecret raid were still tense when the planes took off mid-afternoon Sunday.

Israeli officials have refused to disclose the exact route that the planes used, but they are understood to have taken off from the Etzion Air Base near Eilat, on the northern tip of the Gulf of Aqaba, and flown an indirect route over Saudi Arabia, apparently bypassing Jordan.

There were some reports in Jerusalem among foreign observers that the pilots on the mission communicated among themselves in Arabic, apparently to avoid raising suspicions and to give the impression that they were Jordanian.

Despite the length of the trip, the planes apparently avoided detection until reaching the Iraqi border, about 250 miles from their target, where the Iraqis offered sporadic antiaircraft fire, the Israeli officials said. But they added that no surface-to-air missiles were fired and no Iraqi aircraft attempted to intercept the mission. No Israeli planes were hit, they said.

The Israelis surprised the Iraqis by flying in from the south over the usually quiet Saudi border, rather than from due west, the most direct route from Israel, a high-level Paris source said. The attack began, just as the sun was beginning to set about 6:40 p.m. in Baghdad.

Israeli military officials said yesterday that the attack, which lasted only two minutes, offered no time for Iraqi interceptors to scramble and put up a fight to save the reactor, 12 miles south of Baghdad.

Officials in France and the United States agreed yesterday that the Israelis used American-supplied planes for the highly controversial raid, which Israeli officials said left three dead. But it was unclear, exactly what types of planes were used.

Pentagon spokesman Henry E. Catto Jr. said eight F16 fighter bombers, each carrying two 2,000-pound bombs, as well as six F15 fighters were used on the raid. The F16, a slight, light craft, uses advanced electronics needed for the type of pinpoint bombing apparently used by the Israelis during the high-altitude flight. The F15, which escorted the bombers for protective cover, is far more advanced than any fighter Iraq currently employs, defense officials said.

French sources reported, however, that three U.S.-made Phantom F4 fighter-bombers carried out the raid from a high altitude. And the Iraqis said that nine planes made the mission.

But the question of how the planes avoided detection raised more of a controversy yesterday. Sources in Paris reported that the Israelis used highly sophisticated U.S.-supplied electronic jamming equipment to blind the Iraqi air defenses.

Since the air strike was apparently conducted from a high altitude and not dive bombing, U.S. sources said, Iraqi antiaircraft missiles may not have been productive. Besides modern air forces, such as Israel's, are equipped with an array of electronic countermeasures to throw such missiles off course.

But much to the embarrassment of the United States, which said it did not know about the raid beforehand, the Israeli jets slipped through Saudi Arabia without being seen by the Airborne Warning and Control System sentry planes stationed there. The Pentagon said the AWACS, which have a range of 350 miles, were on duty at the time but were facing the Persion Gulf to protect against an invasion of the Saudi oil fields from Iran.

U.S. sources also reported that inspectors from the International Atomic Energy Agency in Vienna were on scene and in a position to see for themselves the scale of the damage. The inspectors were in Baghdad to check the enriched uranium fuel for the reactor to make sure the Iraqis had not tampered with it in an attempt to use it to make nuclear explosives, the U.S. sources said.

The French technicians arriving in Paris said the raid caused no nuclear contamination since the highly enriched weapons-grade uranium scheduled for delivery from France had not yet arrived.

At the time of the raid, 26 pounds of the 93 percent enriched uranium already delivered to fuel the smaller reactor was being stored underground in special water-filled storage canals that run between the two reactors, French officials Frenchman insisted, even if there had been a hit on the irradiated uranium bars, only the immediate surroundings would have been contaminated.

The Israelis attempted to destroy the plant before it was loaded with uranium so it could not produce any plutonium once it began operation.