Besieged after five days of war with Iraq, Iranian forces were still putting up determined resistance today from embattled strongholds around the blazing oil refinery of Abadan.

Iranian artillery fire and the crackle of small automatic weapons were clearly audible around the refinery, about 300 yards away from here on the other side of the narrow Shattal-Arab waterway. An Iraqi field officer confirmed that despite earlier government claims that Khorramshahr had already fallen, heavy fighting continued for the Iranian port five miles up the strategic estuary.

The continuing Iranian resistance indicated that despite a slackening of the air war today, the conflict between Iraq and Iran was still far from decided. [Iraqi jets bombed several targets in Tehran late today, news services reported, and an announcement in Baghdad said that the main objective was an Iranian oil refinery on the outskirts of the city. Radio Tehran interrupted its regular broadcasts to warn Iranians near Tehran's Mehrabad Airport to evacuate the area and ordered drivers to turn off their headlights and park their vehicles. Soon afterward, antiaircraft fire roared out, and Tehran's electricity was cut off.][The Iraqi government announced, meanwhile, that Iranian warplanes bombed oil installations at Kirkuk in northern Iraq and hit other targets at Mosul and Quayyara in the same region.] [Iran retaliated for the Iraqi bombing of Tehran with a predawn air raid Saturday on southeastern Baghdad, the Associated Press reported from the Iraqi capital. Witnesses said they believed the strike was aimed at a military base and said the attackers were met by antiaircraft fire that lit up the sky.]

Throughout the day Iraqi artillery, dug in among the thick palm groves behind this now abandoned and rubble-strewn mud brick village on the south bank of the Shatt-al-Arab, poured a steady stream of whistling shells into the flaming Abadan oil installations. Billowing clouds of gray-black smoke rose 3,000 feet into the sky.

From the opposite bank of the waterway, there could be heard, amid the thump of artillery shells and the roar of flames, the hollow rattle of automatic rifle fire testifying that fighting was still going on around the refinery defense perimeter three days after the Iraqi government first announced that Abadan and Khorramshahr were surrounded and beseiged.

At one point during the day, an eerie quiet suddenly fell over the village of Seiba, as if the war had been suspended. For a few minutes, the only sounds discernible were the distant quack of ducks and the cluck of a rooster left behind by fleeting villagers when the war for Abadan bagan earlier in the week.

Then the war resumed with a vengeance as two Iranian artillery shells slammed into the village's main street with deafening blasts. Sharapnel and bits of concrete and rock spattered the walls nearby, leaving behind a pall of acrid cordite smoke to sear the throats of the few soldiers and journalists crouched behind a brick wall watching the action across the river.

The shelling of Iraqi positions in Seiba, and the longer range artillery shells, which overflew the town from time to time to crash in the sandy desert a few miles to the rear where an Iraqi communications unit was dug in with its vehicles, was proof enough that the Iranian forces holding on to the Abadan refinery, the largest in the Middle East and the keystone of Iran's economy, were far from beaten.

Confirmation of the surprising tenacity of Iran's purge-weakened army came later in the day from the Iraqi tank corps captain regrouping his tanks from the Khorramshahr front of the left bank of the Shatt-al-Arab across from Basra. The captain, covered with dust but seemingly confident about Iraqi progress, confirmed that heavy fighting was still going on for Khorramshahr and that Iraqi troops had yet to capture it.

"The fighting is intense," he said.

About four days of air raids in and around Iranian and Iraqi oil facilities next to the contested waterway that separates the two countries, there was little air activity in this region today.

In Basra, Iraq's petrochemical center 30 miles behind the front, there were no air raids, although a couple of false warnings sent the city sirens screaming and guns popping in the air in the late afternoon.

The air had been vicious in the first days of the conflict. Iraqi hospital directors in Basra told journalists that in the first four days of the fighting, around 100 civilians were killed and about 500 injured in and around the port city by Iranian jets strafing and bombing the city and its petrochemical industries.

Hospital officials said at least 50 percent of the civilian casualties had been children. Many, unaware of the danger from passing planes, ran into the streets or onto their house roofs to watch the action in the air.

After showing visitors through the pediatric ward of Republican Hospital in Basra, where children lay with amputated limbs, shrapnel-lacerated abdomens, or hanging in traction from concussion breaks, Dr. Behnan Saign, the surgeon in charge of the hospital emergency unit, said:

"The bombing of civilians must have been deliberate. Most of our patients came from residential districts far from industrial or military targets."

Doctors admitted, however, that since yesterday morning there had been only one new civilian casualty from the Iranian air strikes, a man brought in with a machine-gun shell in the chest.

The lack of Iranian air raids restored a semblance of normality to Basra. Traffic, while still far below normal, sped through the streets throughout the day.