Amid signs that its Army's superior firepower was finally beginning to wear down the Iranian resistance, Iraq today intensified its drive to take the shell-smashed Iranian port city of Khorramshahr, fighting house to house toward the heart of the city while consolidating its hold on the port's smoldering dockyards along the Shatt-al-Arab waterway.

The new Iraqi drive to capture the important commercial port city, which has resisted the Iraqi assaults for two weeks, came only hours after Iraq's efforts to establish a unilateral cease-fire in place yesterday collapsed because of Iranian refusal to stop shooting as long as Iraqi forces remain on Iranian soil.

The Iraqi push coincided with the heaviest Iraqi air attack on Tehran since the start of the Persian Gulf war. Iraqi planes, believed to be Mig fighter-bombers, swooped on Tehran shortly before dusk and struck its international airport and oil refinery, Reuter news agency reported from the Iranian capital. Iraqi authorities said the raid came in retaliation for "satanic" attacks by Iran on civilian targets.

The official Tehran radio reported that four Iranians were killed in the bombing.

According to Iranian airport sources, a military aircraft service center at one end of the Mehrabad International Airport complex was hit.

A spokesman for the oil refinery on the southern outskirts of Tehran said it sustained no damage. He claimed that two enemy planes were shot down and that the fate of their pilots was not known.

The Tehran refinery, with a capacity of 200,000 barrels a day, has taken on added importance following the closure of the gigantic Abadan refinery in southwestern Iran, badly damaged by two weeks of Iraqi bombardment. However, the main Tehran refinery has been operating at much less than its rated capacity.

Sources at the airport said the fire there was caused by the bombing of a small petrochemical plant in one corner of a helicopter repair works, Reuter reported.

"The satanic tyrants living in Qom and Tehran should know that Iraq is going to teach them a lesson," the Iraqi Revolutionary Command Council said in its 61st communique of the 15-day war. "We will shake the earth beneath their feet."

A second council communique in Baghdad today claimed that in battles all along the central and southern border fronts inside Iran, Iraqi forces killed 18 Iranians, wounded 48 others, knocked out 25 tanks and one missile launcher and shot down four Iranian planes. Iraqi losses, the communique said, were 16 killed, three missing, 23 wounded, three tanks destroyed and two artillery pieces hit.

The main war front, as it has been throughout the war, continued to be along the northern banks of the Shatt-al-Arab waterway at Khorramshahr and its neighboring oil refinery complex city of Abadan, nine miles to the east.

Iraqi statements spoke of "fierce house-to-house fighting" in Khorramshahr since Sunday night when the new assault on the city began after the cease-fire collapsed.

Western correspondents who managed to get to the port dockyards early today said they were firmly in Iraqi hands, although sporadic mortar and sniper fire was still coming into the dock area. The correspondents also reported that artillery fire continued to fall on the city center to the north, where Iranian Revolutionary Guards, backed by Iranian Army units with Chieftain tanks, were still entrenched.

At Khorramshahr's dock, two small coastal freighters were said to be burning out of control. They and six larger ocean freighters all showed varying amounts of shell and gunfire damage. The ships and their crews have been trapped in the port since the hostilities began between the two OPEC nations Sept. 22.

Iraqi Army officers in Khorramshahr spoke confidently of being able to carry their offensive across the Karun River behind the port in the coming days to push toward Abadan, whose vast oil installations have been burning out of control now for two weeks from Iraqi bombings and shellings.

To push on to Abadan, the Iraqi forces still must dislodge Iranians in the heart of Khorramshahr who are blocking the way to the one bridge over the Karun River. The Iraqis must capture this bridge before they can assault Abadan, where Iranian resistance is expected to be as tenacious as in Khorramshahr.

Despite the optimism expressed by officers in Khorramshahr, the military command in Baghdad, reflecting a new official candor imposed over the weekend by Defense Minister Adnan Khairallah, has so far refrained from making any claim that Khorramshahr has finally been taken.

Although the river port's strategic value to Iran has diminished because of its virtual isolation in the first days of the war, the fall of Khorramshahr would still be a major psychological boost to Iraq and would represent its first major victory in the war.

The fall of Khorramshahr would also prove a timely boost to President Saddam Hussein, who apparently misjudged the ease with which he could humble his Iranian neighbors, traditional enemies since the Arabs pushed the Iranians out of what is now Iraq after the battle of Qadisiyah in 635.

While ancient enmity, religious differences and territorial disputes around the Shatt-at-Arab lie behind the war between Iraq and Iran, another major factor is Saddam Hussein's own ambitions to establish his nation of 12.5 million people as the major power in the Persian Gulf region -- once dominated by the late shah of Iran -- as well as to project himself as the leader of the Arab world as a whole.

In almost endless messages of support from abroad read with the nightly news, Hussein is being depicted as the greatest Arab leader since the late Gamal Abdel Nasser of Egypt. As one message from an Arab Baath Socialist Party cell in Sri Lanka put it: "Saddam Hussein is the leader of the Arab nation, the brave knight of the Arabs."

In Jordan, King Hussein said tonight that Iraq's victory over Iran would mark the beginning of "victory here in Palestine," Reuter reported from Amman.

In Khorramshahr, United Press International reported that journalists watched Iraqis haul away war booty from dockside containers -- bicycles, vacuum cleaners, furniture and other portable household goods. One Iraqi junior officer stuffed a large plastic bag full of orange and yellow baseball caps, hot plates and electric fans.

Iraqi troops, with Khorramshahr's port area along the strategic Shatt-al-Arab waterway in firm control, surrounded the city center and seemed content to starve out the few Iranian defenders left there, UPI reported.