DUBAI, UNITED ARAB EMIRATES, OCT. 28 -- Iraq broke a week-long lull in the Persian Gulf tanker war with air attacks on three "maritime targets" off the Iranian coast in the past 24 hours, in a move that may presage a new round of tit-for-tat warfare.

The new Iraqi air strikes in the gulf came 12 hours after Baghdad unleashed a new bombing campaign against Iran's vital oil installations to "deprive the Iranian regime of its mainstays of aggression."

Iran charged that Iraqi planes also attacked two "nonmilitary" targets in its western Khuzestan and southern Fars provinces, and it warned Iraqi civilians to seek refuge in four Shiite holy cities to avoid its "deadly response."

The terms used by the Iranian warning, broadcast on Tehran radio, were similar to warnings issued earlier this month before Iran fired four Soviet-made Scud missiles into the heart of Baghdad. Iraq claimed that 134 Iraqis were killed and 2,036 wounded as a result of the missiles, one of which fell on a school full of children.

"The rulers of Baghdad should anticipate the deadly response of combatants of Islam as long as they continue their wicked acts," the Iranian statement said. It warned all Iraqi civilians living near "military, economic and industrial establishments" to abandon their homes as "quickly as possible" and seek refuge in the holy cities of Najaf, Karbala, Kadhimain and Samarra "so that they may not be harmed in the course of the deterrent operations."

An Iraqi military communique tonight said its Air Force had staged a series of "destructive raids" on oil refineries and chemical plants in and around the city of Shiraz, in Iran's southwest.

The Iraqi communique said, "Iraq is resolved to deprive the Iranian regime of its mainstays of aggression and factors contributing to its continuation of the war."

Iran claimed that it shot down two Iraqi jets during the raids, but the Iraqi communique denied any losses and said all Iraqi planes had returned to base safely.

Meanwhile, a Soviet deputy foreign minister, Yuli Vorontsov, arrived in Baghdad on a trip that also will take him to Tehran and Kuwait. Diplomatic sources described Vorontsov's mission as an attempt to win Iranian acceptance of the cease-fire resolution adopted by the U.N. Security Council in July.

{In another development, fire broke out Wednesday afternoon at Saudi Arabia's Safaniya oil field in the northern gulf. A Washington spokesman for Aramco, which operates the offshore oil field, said the fire started after an Aramco supply boat accidentally ruptured a pipeline eight miles off the Saudi coast. A tanker pilot said the fire was put out Wednesday night, Reuter reported.}

Iraq resumed its attacks on the Iranian oil industry yesterday with an air raid on the Agha Jari oil fields. It followed that with today's raids around Shiraz and the resumption of air attacks on shipping in the gulf late last night and early today.

The Iraqi communique referred to "very large" and "large maritime targets," terms that Baghdad usually uses for supertankers and tankers. Shipping officials here said they did not know what the Iraqi-attacked "maritime targets" were.

That was taken as an indicator that the Iraqi attacks were not on international shipping but more likely on decoys that Iran has set around its main oil terminals and shipping routes or on National Iranian Oil Co. tankers used to shuttle petroleum to safer loading terminals near the Strait of Hormuz.

Since Iraq decided to hit at Iran's oil export lifeline in 1984, hundreds of ships have been hit by French-made Exocet missiles fired from Iraqi planes or in Iranian retaliatory attacks against ships serving Arab gulf nations that support Iraq in the seven-year-old war.

Meanwhile, Iranian President Ali Khamenei shrugged off the U.S. trade embargo against Iran announced by President Reagan on Monday. In a speech broadcast on Tehran radio, Khamenei said Iran would withstand whatever "pressure" Washington sought to apply and would give an "appropriate reply" to the U.S. action.

"We have been threatened with an economic blockade by the western states," he said. "We are not afraid of such things."

Khamenei's statement was the second official expression of defiance of the U.S. embargo. Yesterday Prime Minister Mir Hossein Mousavi dismissed the economic sanctions as unimportant, calling them "mere cosmetic measures" for "U.S. domestic consumption in view of recent events in the gulf and the unprecedented nose dive of the stock market."