Despite stiff resistance by Iranian tanks and helicopter gunships, Iraqi forces behind relentless artillery barrages pushed today to within two miles of Abadan and its giant oil refinery, the Iraqi command announced.

The Army said it had established an irregular front around the northern and eastern sectors of Abadan and was expanding the line amid heavy fire from Iranian defenders. Iraqi artillery emplacements outside Khorramshahr, about 10 miles to the north, continued to pound Abadan to soften resistance to the assault by Iraqi ground troops. A television cameraman who visited the city said nasty black smoke from oil fires clouded the sky.

As it did last week at Khorramshahr, the Iraqi army appeared to be forming a noose around Abadan, sniping and cannonading the city and its oil installations but avoiding a direct attack that would be likely to involve bloody house-to-house fighting with Iranian soldiers and Revolutionary Guards.

The official Iranian news agency, Pars, reported that 30 civilians were killed and 140 were wounded in a nightlong artillery barrage directed at the city, site of the largest oil refinery in the Middle East with a capacity before the war of 610,000 barrels a day but now heavily damaged and shut down.

The Iraqi forces also were reported to be blowing up Iranian oil pipelines as they advanced, in an apparent effort to prevent Abadan's crude oil from reaching other refineries that may still be producing fuel for the Iranian war effort. Western newsmen saw orange flames leaping from a major north-south pipeline near Abadan after it was blasted by Iraqi troops. Elsewhere on the pipeline, crude oil spilled onto the ground, they said.

The Iraqi command said its forces also destroyed an oil pumping station and a "pipeline network" at Ahwaz, a major communications hub for rail, road and pipeline traffic about 75 miles north of Abadan and 60 miles east of the Iranian-Iraqi border.

The main breach in Iranian defenses along the Shatt-al-Arab waterway was the 250-yard-long Karun River bridge which, according to the Western visitors to the site, has been secured by the Iraqis. In addition, the Iraqis have cut off the main road between Khorramshahr and Ahwaz, over which supplies have been moving to Abadan's defenders since the war began 22 days ago.

The Iranians also appeared unable to provide adequate air support to their beleaguered troops in Khorramshahr and Abadan, either because of inability to get their F4 Phantom and F5 fighters off the ground or because of a lack of coordination with the ground forces.

But President Abol Hassan Bani-Sadr said on Tehran Radio that Iranian warplanes and helicopters have "routed the enemy" after being prevented from effective action Saturday by bad weather. Few Iranian jets were seen in the sky here, however, and Bani-Sadr gave no details. But Iran has a large fleet of U.S.-designed Cobra helicopter gunships acquired during the reign of the late shah.

The Cobra gunships, which can strafe advancing troops with a withering hail of bullets, have not previously been reported in wide use against Iraqi forces. Many are thought to be grounded for lace of maintenance. The Iraqi command announced in Baghdad that two were shot down near Abadan in today's fighting.

[Bani-Sadr told U.N. Secretary General Kurt Waldheim, meanwhile, that Iran wants to keep the Shatt-al-Arab waterway open for "lawful international commerce." His statement, in a message to Waldheim and reported by news agencies, was a reply to a U.N. appeal that ships trapped in the fighting be allowed to exit into the Persian Gulf flying the U.N. flag as a gesture of their peaceful intent. A U.N. spokesman said Iraq also was expected to reply to the appeal soon.]

The Western reporters, among a few allowed to the front today by Iraqi officers, said a pontoon bridge spanning the Karun River -- a tributary of the Shatt-al-Arab -- had been used to move numerous tanks and other heavy equipment closer to Abadan. But there was no indication when and if the Iraqis would make their final move on Abadan.

The Iraqi army was said to have established secure positions on the other side of the Karun, although Iranian artillery batteries in Abadan continued to shell the area of the pontoon crossing. Most of the shells were reported to have fallen wide of the bridge.

The Iraqis have moved so much of their own equipment across the span that they also have begun to use it for transporting captured Iranian trucks back to the Iraqi rear positions. Independent witnesses said the Iraqis were dug in on the other side of the Karun and that there was no discernible resistance at the bridge.