DUBAI, UNITED ARAB EMIRATES, SEPT. 2 (WEDNESDAY) -- Iraq escalated its latest aerial offensive against Iran yesterday by bombing four more vessels carrying Iranian oil and attacking industrial plants near two cities, while Iranian gunboats retaliated by firing rockets at three tankers and a cargo ship.

Iran said it also shot down an Iraqi warplane in a dogfight over the gulf, but Iraq denied the claim. Following the fourth day of Iraqi air raids that broke a six-week de facto truce in the "tanker war," Iran vowed to conduct new reprisals against Iraqi military and industrial targets that could also endanger civilian centers.

Iraq said its warplanes hit four Iranian tankers yesterday, bringing to nine the number of vessels it says it has struck since ending the truce Saturday. Iran launched reprisal raids against four ships, most of them transporting Arab oil.

Yesterday, gunboats attacked the Spanish ship Munguia igniting a fire in the engine room, but no serious damage was reported. The Associated Press reported that the 300,000-ton supertanker was loaded with 2.1 million barrels of Saudi Arabian crude when it was hit.

Last night, and early today speedboats believed to be Iranian, fired at a South Korean-owned tanker, a Japanese tanker and a Cypriot cargo ship, inflicting only light damage to each of the vessels. The South Korean tanker Astro Pegasus and the Japanese tanker Diamond Marine headed to Dubai for repairs; the Cypriot cargo ship Leonidas Glory needed no assistance, according to Lloyd's of London.

{In Washington, Pentagon officials said crewmen aboard the helicopter carrier USS Guadalcanal rescued an Iraqi pilot whose F1 Mirage fighter jet had crashed in the gulf on Saturday. Story on Page A18.

{Pentagon officials also said the battleship USS Missouri arrived today in the northern Arabian Sea with five other ships comprising its battle group.}

As the United States resumed its naval buildup in the region, Iran appeared to be directing its reprisal attacks away from the U.S. Navy ships escorting reflagged Kuwaiti tankers in the gulf.

For two days, Iran and Iraq have traded threats of renewed attacks on each other's cities, but Iran's only confirmed acts of retaliation so far have been on unescorted ships.

Tehran radio accused Iraq of having bombed civilian areas in southwestern Khuzestan Province and the central city of Isfahan. Tehran warned Iraqi citizens to move away from industrial centers, which it said it would attack. Iran and Iraq have abstained from campaigns against cities since last February, when heavy rocket and bomb attacks on each other's civilian centers caused thousands of casualties.

Since Sunday, Iraq has claimed attacks on nine "large naval targets" -- normally a reference to oil tankers or other merchant ships -- but the difficulty of verifying attacks, especially in Iranian waters, left it unclear how many ships have actually been hit.

{The Iraqi Embassy charge d'affaires in London was summoned to the British Foreign Office Tuesday and told "in the strongest terms" that Iraq must "refrain from military action which would serve only to escalate hostilities and jeopardize diplomatic efforts aimed at bringing about a negotiated solution to the conflict," a Foreign Office spokesman said, according to United Press International.}

Iraq asserts that Iran has deliberately avoided accepting or rejecting the U.N. Security Council's cease-fire resolution of July 20 because the de facto maritime truce has enabled Iran to increase its oil exports. Iraq repeated today that it "will not give Iran another chance . . . to continue exporting its oil to finance aggression against Iraq."

Analysts in the region say that Iraq's strategy in renewing its maritime attacks is to keep the war focused in the gulf, where world media attention is concentrated on the U.S. naval buildup, rather than on Baghdad's long land war front with Iran.

The analysts, interviewed here and by telephone from other gulf cities, differed over whether Iraq resumed its "tanker war" with the specific aim of provoking Iranian retaliation that would embroil the U.S. Navy in a direct confrontation.

Many analysts questioned Iraq's stated rationale for resuming its attacks on Iranian tankers and oil terminals: that it is trying to prevent Iran's reaping a windfall from unfettered oil exports, which in turn help finance Tehran's war effort.

"Iraq wants to fight this war in the gulf as a way of broadening it," said an American analyst in a gulf capital. "Attacks in the gulf get headlines, cause tremors in the business community" and increase chances that the outside world will keep pressing Iran for a truce, he said. "Fighting on the land front gets you an inch of news on the inside pages," the analyst added.

Other observers said Iraqi attacks have never substantially affected Iran's oil exports, except for short-term disruptions during periods of intense bombing. They suggested that -- perhaps by design -- Iraq's moves in the gulf are more likely to drag U.S. forces into the fighting than to choke Iran economically.