Iraq and Iran engaged in tenacious battles around the key Iranian oil center of Abadan yesterday as the Iranian Air Force pounded at least eight targets across Iraq in the 24th day of war between the two Middle East oil producers.

As the fighting raged at the front, Iran said its Islamic fundamentalist prime minister, Mohammed Ali Rajai, would arrive in New York today at the head of a four-man delegation to represent it in the U.N. Security Council debate on the Persian Gulf war.

News service reports from the main front along the strategic Shattal-Arab estuary indicated that Iraqi infantry and armored units were intensifying their drive on Abadan and the towns of Ahwaz and Dezful, but were encountering stiff resistance.

The fighting for the oil centers in Khuzestan Province appeared to be part of an Iraqi drive aimed at cutting off oil supplies to Tehran and northern Iran.

For its part, Iran bombed Baghdad and other Iraqi cities for the second day running, and Tehran radio said more than 1,000 Iraqi soliders were killed in a series of "lightning attacks" on the northern end of Iraq's invasion front.

According to the Tehran radio report on yesterday's reported Iranian battle victories, members of the airborne division overran two enemy bases and destroyed 11 tanks in the Ilam sector, about 250 miles northwest of the primary battle area centered at Abadan. There was no confirmation of the report, which, if true, would seem to indicate that the Iranians were capable of lauching a major counterattack.

The surprise Iranian announcement of Rajai's trip to the United Nations was seen by Western diplomats in New York as a significant development because it may mean Iran was at least beginning to end its isolation. Iran also attended the Security Council debated yesterday for the first time since the Iranian revolution that overthrew the late shah in February 1979.

One ranking U.S. official at the United Nations called the two developments most significant "both from the point of view of the war and of the hostage crisis." He noted that Rajai "represents a faction in Iranian politics separate from that of Presidewnt [Abol Hassan] Bani-Sadr. His participation is more important than if Bandi-Sadr had come. It means that both factions are now ready to deal with the international community."

After the Iranian representative, Ali Shams Ardakani, delivered a short statement saying Rajai was coming and asking the Security Council to reconvene Friday, the council set the debate for 3:30 p.m. Friday.

Ardakani told reporters after the council meeting that Rajai's visit "is the acid test for the Third World to see how the U.N. could secure the rights and integrity of its members and secure peace by pushing back the violators."

He said Iran would ask the council be called "the exportation of the Iranian revolution, to make the message of this revolution understood by everybody."

The Iraqi representative, Foreign Minister Saadoun Hammadi, reiterated his government's willingness to protect "the conomic interests of other nations to the best of our ability," and noted that Iraq had "responded positively to appeals addressed to us and to proposals for a cease-fire."

According to Iraqi military communiques quoted by Reuter, Iranian fighter-bombers struck Baghdad and seven other places in central, southern and northern Iraq -- one of the most intensive Iranian Air Force actions since the Persian Gulf war began Sept. 22.

The Iraqis attached an oil refinery in the northern Iranian city of Tabriz, not far from the Soviet border. According to Reuter, Iraqi fighters also attacked troop concentrations near the important communications center of Dezful, which is astride most of the pipelines running from the southern oil fields north to Tehran.

The Iraqi military said intense fighting continued on all fronts and said 158 Iranians were killed in battle yesterday -- one of the highest daily totals claimed to date. The Iraqi High Command said four Iranian aircraft had been shot down, Reuter reported, and Tehran radio likewise claimed that four Iraqi warplanes were downed yesterday.

Although experts in the Persian Gulf region generally view casualty claims with caution, they are seen as a measure of the war's intensity.

On the Iranian side, the Associated Press reported that a spokesman for the Abadan governor's office said the Iraqis had been stopped less than five miles from the crucial oil city and that the battle was continuing, according to the official Pars News Agency. A Pars correspondent reported that the Iraqi forces "are now in a trap with no way of escaping."

Only one road was reported still open into Abadan, AP added, the highway on the east to the oil fields on the northeast coast of the Persian Gulf. There were unconfirmed reports that Iran was sending in reinforcements including heavy artillery over this route. But no heavy or effective Iranian shelling was seen Tuesday by the reporters touring the Iraqi side of the battlefront.

An Iraqi communique late Tuesday night claimed Iraqi forces had cut the pipeline between the eastern fileds and Abadan. The pipeline presumably was already shut down since Iraqi shelling and air attacks set the Abadan refinery afire and stopped its operations early in the 24-day-old war for control of the Shatt-al-Arab.

There was speculation that the Iraqis, to minimize casualties, would use the same tactics on Abadan that they are using to the port city of Khorramshahr 10 miles to the northwest, keeping the Iranian defenders under siege and constant artillery attack and waiting for them to run out of food and ammunition rather than trying to overcome them in close combat.

Abadan, 30 miles north of the gulf, and Khorramshahr are the two key points on the Iranian side of the Shatt, Iraq's waterway to the gulf and a major territorial issue for centuries between the Arabs of what is now Iraq and the Persians of Iran.

The Iranians yesterday also threatened to mine the Persian Gulf and the strategic Strait of Hormuz, through which most of the oil to the West from the gulf regions flows.

Iraq's news agency, meanwhile, said President Saddam Hussein had told U.N. Secretary General Kurt Waldheim that Iraq had begun evacuating foreign ships from the big port of Khorramshahr. This report was seen as tantamount to Iraqi rejection of Waldheim's request for a limited truce so foreign ships stranded in the Shatt-al-Arab could leave. Iran earlier said it would go along with such a cease-fire.