Eighteen minutes after the 6 a.m. work shift began at Iraq's sprawling Basra petrochemicals complex No. 1 at the town of Zubair, two Iranian F4 Phantom jets roared out of the lightening sky at roof level.

No one who was there can now be sure whether five or six bombs were dropped in that one terrorizing dawn raid yesterday but, when the planes streaked off, more than 10 foreign technicians were dead, including at least three Americans, and scores of Iraqi workmen lay bleeding and dying across the plant grounds, according to survivors who have reached safety in Kuwait.

The raid sent the American technicians working at the site fleeing here to Kuwait. Their eyewitness accounts today provided the first detailed look at the front lines of this strange war -- the oil industries of both countries.

For the first time in a Middle East conflict, the oil fields and refineries, and the foreign technicians who work there, have become the key targets, with each side apparently determined to inflict massive economic damage on the other. That damage, if extensive enough, would reach out to affect Western consumers as well.

It was a raid, like dozens of others on Iraqi industrial targets, which proved that, far from being down and out, the Iranian Air Force -- and at least some of its sophisticated U.S.-provided jets -- is very much operational. Before the day was out, they had, from all reports, dealt a potential death blow to Iraq's vital oil industry gathered around the vulnerable port city of Basra, at the mouth of the Persian Gulf.

According to reports from the hundreds of foreign survivors who fled here, Iraq's main oil industry has been put to flame and destruction by the Iranian Phantoms which seemed to roam the skies over Basra at random.

Many refugees grumbled about the fact that authorities at the Zubair petrochemical plant waited until it was attacked before shutting down and evacuating.

"We had been watching shelling, aerial dogfights, tracers, and antiaircraft fire through the night as close to a mile north and south of us for at least a day before we were hit," complained Dan Gage, of Houston, who accused company management of "being more interested in profits than human lives."

While the Zubair plant was clearly the biggest industrial establishment in the area run by foreigners, it was hardly the only one. Close on the heels of the Zubair refugees came a group of some 400 Italians who had been building and expanding a refinery at Shuaiba, which was first bombed Monday and today was reported destroyed.

Another U.s. refugee arriving here this afternoon, Tony Smilko, a Houston oil consultant who had been working at the national Iraqi oil company refinery at Birgisia, 12 miles from Basra, reported that the refinery was blown up in air raids late Tuesday. "There isn't much left of the oil industry around Basra that I could see," he said.

The raid on the plant at Zubair, Iraq's most advanced and sophisticated industrial establishment, was considered typical rather than an exception. Even though the first bombing run did not totally destroy the complex, it sowed death and fear and forced the plant's immediate closure.

British supervisor Jim Stevenson, and Harvey Johnson, of Houston, had barely got to the plant's maintenance garage they supervised when the first Iranian bomb scored a direct hit, killing them, and at least a dozen other plant workers instantly, witnesses said.

In his quarters in the vast 300-room singles residence nearby, British insurance assessor Ronald Richey and his British assistant, both of Lloyds of London, did not even know what hit them when the second bomb struck their room in the residence's southeast wing.

When Tim Heard, another supervisor from Houston, pushed through the wreckage to try to find them, he said, "I kicked open the door and found only half a body -- fragments of the other one were scattered in the courtyard outside."

More lucky was a Texas woman and her teen-age daughter, both of whom preferred to remain anonymous, who lived in a nearby area of family housing. They were in the back room when another bomb, believed by ordnance experts to be a 250-pounder, hit the front of their house. Both were blown through the back window but escaped with only minor face cuts. Miraculously none of the dozens of other women and children in the plant area was injured.

Another lucky survivor was Raymond de Luna from Woodlands, Texas, who was at work in the plant's loading area when the planes roared in. He ran to the courtyard in time to be bowled over by the first concussion, he said. He had barely gotten to his feet when a second explosion broke his right leg. "I'm just lucky to be alive," he said.

"We got the s. .t bombed out of us," recalled Ron Crawford, a burly, bearded service engineer from Tulsa, Okla., who had just left his room to make a telephone call when they bombed it.

"I rushed back to my room to find it a shambles, with the door just barely hanging on its hinges,' 'he said after making his way to Kuwait along with a flood of foreign refugees. "I kicked down the door only to find that my suitcase was blown up and my guitar was broke."

Fire soon reduced the "motel" to smoldering ruins.

Given the confusion that followed, no one is as yet clear as to the exact number of casualties and, since the plant was evacuated in a near panic within hours, of the total damage from raids that are believed to have followed.

But aside from the residential motel and the maintenance complex, it is known that its sophisticated low-density polyethylene unit was destroyed and its gas and diesel storage area set aflame.

U.S. officials in Kuwait helped process the refugees, many of whom brought no passports or identifying papers in their hasty flight to the Kuwait border in a motley convoy of company cars and trucks, The officials refused to give any exact information beyond admitting that 154 Americans, all from Zubair, had been processed at the border for entry into Kuwait within the last 24 hours.

U.S. Charge d'Affaires Brooks Wrambelmeier denied that the embassy had any precise information despite the fact that his consular officials had been dispatched to the border to debrief the refugees. "I don't know anything about casualities," he said. "You will have to check that out in Basra or Baghdad."

Officials of the Lummus Combustion Engineering Co. of Bloomfield, N.J., the main contractor for the 400 foreign expatriate technicians at the Zubair complex, were only slightly more informative.

One senior company official admitted that at least six of his employees -- three Americans, two British and one Indian or Pakistani -- were missing, and presumed dead.

He said that two persons working at the plant for the West German firm A.E.G., presumably Germans, also were missing.

The refugees, most of whom had to spend up to 20 hours at the Iraqi-Kuwaiti border after their ordeal, trying to get temporary Kuwaiti entry papers, were bused here eventually and put up in local hotels pending charter flights out to Europe.

A Reuter correspondent added from the Iraqi-Kuwaiti border:

Soviet personnel have joined the swelling ranks of foreigners fleeing southern Iraq, eyewitnesses said.

"About 500 Russians crossed into Kuwait today," a Polish technician said on arrival at the border post of Abdali.

Officials at the overcrowded border post, trying to cope with a vast increase in the normal number of travelers, refused to be specific when asked if Russians were among the refugees.

"People of many nationalities are coming across. We are too busy to give you details," said a white-robed officer.

No Russians were identifiable among about 3,000 refugees, most of them East European and Asian, gathered at the border post. The Soviet group was believed to have been employed at Iraq's richest oil fields at Rumailah.