Iraqi jets made a daring daylight raid Saturday on an Iranian oil loading facility, their missiles making a "total wreck" of the world's largest operational ship and damaging three other tankers, leaving 18 sailors missing and wounding scores, shipping sources said.

The sources said the raid, Iraq's biggest since a similar attack in December, left the unarmed ships blazing and oozing Iranian oil into the sea as they lay anchored side by side at Iran's Larak Island loading terminal in the Strait of Hormuz, the strategic mouth of the Persian Gulf.Rescue tug boats risked attack to carry survivors - many seriously injured - from the scene to hospitals in Iran's nearby port of Bandar Ab-bas, said shipping sources who monitor Persian Gulf developments during the 71/2-year-old Iran-Iraq war.

The sources said 36 of the 50 crew of the Seawise Giant - the Liberian-registered, 564,739-ton tanker and the largest operational vessel in the world - were picked up and were being taken to Iran.

"Steam tanker Seawise Giant is hit . . . and is a total wreck," the London-based shipping insurer Lloyd's of London reported.

The raid left 14 Seawise Giant crew members unaccounted for, and at least four sailors missing from the Spanish-flagged tanker Barcelona - also a target in the raid.

The sources said the noon attack against the British-flagged, 457,841-ton supertanker Burmah Endeavour and the Seawise Giant came seconds after strikes on the smaller tankers Barcelona and the Cypriot-registered Argosy.

The Barcelona was reported "sinking" after the raid.

Lloyd's said blazes aboard the Seawise Giant and the Argosy were "out of control," and shippers said they saw "billowing pillars of smoke and flames shoot up into the sky."

The sources said Iran's gunners remained silent and its air force failed to scramble to engage the Iraqi jets, which attacked the four ships as they lay anchored "like sitting ducks."

"Air alert," cried the skipper of the Seawise Giant before Iraqi missiles slammed with a deafening roar into his vessel, according to one shipping source, who also said the missile turned the ship "into a ball of fire."

A U.S. Central Command spokesman said there was no U.S. involvement in the incident, but added, "Once again, it looks like the Iranians were caught with their pants down."

In Baghdad, state-run radio and television interrupted normal programs to bring news of the "courageous" and "precisely planned" operation.

A military spokesman said a "very large number of Iraqi jetfighters unleashed rockets" on "giant oil tankers" at Larak.

The spokesman said the jets succeeded "in surprising the enemy and violating his air defenses, attacking the tankers loaded with Iranian oil and setting them ablaze."

There was no immediate reaction from Iran on the damaging raid, which came only days after Iraqi jets shot two Exocet missiles into another Iranian ship, wounding 11 crew members.

Iraq says its attacks on Iranian vessels or neutral ships in Iranian service are intended to dry up Iranian oil export revenues which "feed the Iranian war machine."

There have been no reported Iranian attacks on merchant mariners in the gulf since the Reagan administration last month announced it was extending U.S. naval protection to neutral ships. Previously, the United States had only protected ships flying the U.S. flag but the protection was expanded after a clash last month between U.S. and Iranian forces.

U.S. forces April 18 knocked out two Iranian oil platforms after a mine that U.S. officials said was planted by Iran damaged a U.S. ship. The platform attacks led to clashes between U.S. and Iranian vessels that sank or damaged six Iranian crafts and, according to Tehran, killed 15 Iranian sailors.