Iranian armed forces and Revolutionary Guards attacked Iraqi units along their central front yesterday and claimed to have recaptured 90 square miles of territory, including the strategic heights overlooking the highway to the Iraqi capital, according to Iranian broadcasts.

Iraq said its forces had beaten back the attackers but U.S. analysts said that if past Iranian claims in the long-running war are any example, the Iranians may well have succeeded in recapturing the Iranian hills overlooking the Iraqi border town of Mandali, 70 miles from Baghdad.

There were no reliable casualty reports. The attack came after Iran moved 5,000 to 10,000 regular troops from the southern front, where the two countries fought to a standstill in July and early August, according to the analysts. The troops were joined by an unknown number of irregular Revolutionary Guards and were opposed by 10,000 to 20,000 well-armed and dug-in Iraqis backed by tanks and artillery.

The see-saw war between the two onetime oil powers has lasted two years and has cost thousands of lives in major battles in both Iranian and Iraqi territory.

Iraq held the upper hand during much of the first 18 months, but a series of Iranian attacks has since driven the Iraqis back into their own territory. Iranian attempts to thrust into Iraq have been repulsed.

Iraq still holds two small sections of Iranian territory along the central front and the Iranian communique issued after yesterday's fighting indicated the attack was part of a campaign to regain this territory. There was no mention of pushing on into Iraq.

Iran holds a salient of Iraqi territory about two miles deep and 15 miles long opposite Basra in southern Iraq.

U.S. analysts said yesterday's attack could be the prelude to a large-scale campaign or simply a local action to prove the Iranian Army was still in the fight after setbacks suffered several weeks ago in the southern front near Basra. Whichever it proves to be, it indicates continued Iranian ability to keep the Iraqis off balance by shifting the focus of the hostilities.

"The offensive has been launched to liberate territories still occupied by the Iraqi forces, and to show the Iraqi regime that the Islamic republic would continue its fight until it fully obtains its just conditions which it has set for ending the war," an Iranian communique said.

The U.N. Security Council, acting on an Iraqi request, agreed to begin debate Monday on Iraq's complaints against Iran in the war, Reuter reported from the United Nations. Council members made the decision after Iraqi delegate Riyadh Qaysi told them that there had been a serious deterioration in the situation.

Iran has said it wants the return of all Iraqi-captured territory, reparations and the removal of Iraqi President Saddam Hussein before it will agree to an end to hostilities.

Iraq now holds a clear advantage in terms of air superiority, tanks and logistical lines, according to U.S. analysts, but the Iranians have demonstrated a persistence and occasional battlefield ingenuity that has succeeded in pushing the Iraqis out of almost all the territory they had captured at the outset of the war.

Just how far Iran can push the battle from the border area remains unclear. Iraq is now said to be able to put more than 400 fighter planes into the air compared to about 70 for the Iranians, who have been unable to get sufficient spare parts or replacements for the Air Force -- supplied by the United States before the fall of the shah.

Iraq is said to have put up impressive defensive lines in the southern sector that appear capable of repulsing Iranian human-wave attacks.

Iran, on the other hand, has lengthy lines of supply and communications and would have to move tanks and artillery over rugged mountains to mount an extensive offensive in the central sector.

Iranian forces launched yesterday's offensive at 1 a.m., according to an Iranian communique, "immediately achieving . . . their objectives." An Iraqi spokesman said, however, that "after a series of battles," the "Iraqi forces taught the Iranian aggressors new lessons."

U.S. analysts said there was no evidence that air power had figured in the latest battle, most of which seems to have taken place during nighttime hours.

While Iraq generally has been successful in containing the Iranians in recent weeks, Baghdad appears to have been unable to halt the flow of oil from Iran's Khark Island despite repeated air attacks. Warnings against shipping have sent insurance rates for oil shippers soaring.

U.S. sources now say that Iran is continuing to pump between 1 million and 1.5 million barrels daily, with ships continuing to load at Khark. Damage at the huge Iranian oil installation appears to have been limited to destruction of one holding tank.

Iraqi claims to have sunk a number of ships reportedly have not been verified, except for one coastal freighter.