DUBAI, UNITED ARAB EMIRATES, AUG. 17 -- The air and artillery war between Iran and Iraq continued to intensify today with reports of new Iraqi air attacks on Iran's oil installations and artillery barrages fired by Iran at the southern Iraqi city of Basra.

As the main combatants in the seven-year-old Persian Gulf conflict continued their war of attrition, signs were building that a convoy of reflagged Kuwaiti tankers was ready to set sail under the protection of U.S. warships.

Four tankers, now under the U.S. flag, were reported by shipping sources today to have loaded their cargos of crude oil at Kuwaiti ports and were prepared to sail back through the Persian Gulf now that the U.S. Navy has moved minesweeping capability into the region.

Meanwhile, United Nations Secretary General Javier Perez de Cuellar is considering an invitation to visit Tehran for talks on resolving the Iran-Iraq conflict. Perez de Cuellar told Iran's U.N. Ambassador Said Rajaie-Khorassani, who extended the invitation, he was willing to go to Tehran "as long as it would be useful," according to the secretary general's spokesman.

The 18,000-ton U.S. helicopter carrier Guadalcanal arrived in the gulf yesterday carrying eight Sikorsky RH 53D Sea Stallion minesweeping helicopters to help clear the lanes for the return run of the tankers. The Guadalcanal dropped anchor off the island emirate of Bahrain overnight but was reported this evening to have moved to a new position.

Earlier in the day, the Sea Stallions were reported to have carried out exercises to the north of Bahrain in the narrow shipping channels in the northern part of the Persian Gulf, in preparation for protecting Kuwaiti tanker convoys from mines. Because of their size, the large oil tankers have to stick to deep-water channels in the Gulf, restricting them to a very narrow oute and making them more susceptible to hitting mines planted in the shipping lanes.

Four British minesweepers and a supply ship set out today from Scotland, on their way to the gulf to clear mines for British warships accompanying shipping. Also, three French minesweepers and a support ship sailed from the Mediterranean port of Toulon to join an aircraft carrier battle group that reached the Indian Ocean Sunday, United Press International reported.

Iran's state-run radio said Iranian mine-sweeping helicopters discovered several mines in the Gulf of Oman, and exploded them, on the third day of the country's mine-sweeping operations.

The report did not say how many or where the mines were discovered.

With another test of wills between the United States and Iran building over the tankers, an Iraqi military spokesman said that Iranian shelling during the night had killed three persons and wounded seven others at its battered port of Basra.

The spokesman said 42 shells had struck Basra. There was no confirmation of the attack by Iran, but if true, it would represent a re-sumption of the "war of the cities" that racked Iranian and Iraqi civilian centers before it was halted by mutual agreement in February.

Iraq said today its warplanes had attacked Iranian oil targets near the city of Ahwaz for the second straight day, as well as sugar factories in the southern towns of Dezful and Shushtar, but an Iranian communique claimed that the Iraqis struck villages in the area killing nine civilians and wounding scores of others.

The tankers Gas King, Ocean City and Sea Isle city were reported to be waiting fully loaded about two miles off the Al Ahmadi oil terminal while the tanker Bridgeton, damaged by a mine on its entry into the gulf, also was reported to be repaired, loaded and ready to sail.Saudi Accuses Iran of Plot Reuter

MANAMA, Bahrain, Aug. 17 -- Saudi Arabia accused Iranian leaders today of masterminding violence in Mecca on July 31 in which more than 400 people were killed.

A statement read on Saudi television said a Cabinet meeting chaired by King Fahd reviewed security reports of "the sabotage acts planned by the heads of power in Tehran and carried out by Iranian Revolutionary Guards."

{In Tehran, about 2,000 people carrying the bodies of 37 Iranian pilgrims killed in Mecca gathered outside the former U.S. embassy, chanting slogans against America, Saudi Arabia and Israel. The bodies -- among 322 that Iran claims died in the riots -- arrived today from Saudi Arabia.}