Iraq canceled its unilateral cease-fire hours after it began today and unleashed new air strikes and artillery barrages against Iran, which Iraq said had broken the truce earlier with fresh attacks by land, sea and air.

Tonight the Iraqi government vowed to continue its "honorable battle" against its Persian Gulf neighbor and said its forces were "advancing on all fronts" in the two-week-old war.

[In Tehran, Prime Minister Mohammed Ali Rajai claimed that the Soviet Union had offered Iran military aid, but that he had refused it, the state-run Tehran Radio reported. There was no immediate confirmation of the report from Moscow.]

[An Iranian military communique charged that Iraqi warplanes today tried to bomb several targets in Iran, including Tehran's Mehrabad International Airport for the second time in the war. The statement claimed that a lone Soviet-made Iraqi bomber was shot down near the airport.]

The cease-fire, which Iraq began at sunrise today, had been proclaimed by President Saddam Hussein last week in answer to a United Nations Security Council call for a cessation of hostilities between the two nations as a preliminary step toward opening peace negotiations.

Despite Iran's refusal even to consider a cease-fire until Iraqi soldiers withdraw from Iranian territory, Iraqi military officials said their forces had ceased shooting on all fronts at 5 a.m. as scheduled. Iraq had said that it was prepared to maintain the cease-fire for four days if the Iranians would respect it.

Iraqi officials said that two hours after the unilateral cease-fire began, Iranian artillery resumed shelling Iraqi troop positions on several fronts inside Iran. The Iraqi high command said that it waited another 3 1/2 hours to see if the Iranians would quit shooting, but at 11:30 a.m. Iraqi forces were ordered to resume fighting, and the short-lived cease-fire was dead.

Eyewitnesses near the hotly contested Iranian river port of Khorramshahr on the Shatt-al-Arab waterway said that Iraqi firing had begun much earlier there in response to Iranian shelling of their positions in the western corner of the city. By noon, the artillery duels, which have been going on around the besieged port for 11 days now, had resumed their previous intensity.

The Iraqi government also claimed that Iranian jets had staged a series of raids on industrial and military targets around several Iraqi cities this morning before the Iraqi forces resumed fighting.

Here in Basra, a lone Iranian jet fighter-bomber flew over the city shortly after 8 a.m. on a raid against a nearby refinery. However, it was the only air raid of the day against a city that in the first two weeks of the war had been subjected to dozens of air raids or air raid warnings a day.

Iraqi officials said the Iranians had also launched air strikes against the important petroleum center of Kurkuk in northern Iraq.

Late last night, Iraqi Defense Minister Adnan Khairallah indicated at a press conference in Baghdad that Iraq again had softened its terms for a cease-fire with Iran.

Whereas the Iraqis previously had insisted that Iran give up three tiny islands in the Persian Gulf taken from the Arab sheikdoms of Ras al-Khaimah and Sharjah nine years ago, Lt. Gen. Khairallah last night said that for the cease-fire to take effect Iran only had to agree not to shoot on Iraqi forces, send reconnaissance flights over Iraqi territory or concentrate troops near the Iraqi borders.

Khairallah, who had expressed little hope that Iran would honor the cease-fire, said that if the Iranians did not meet those three "minimal" conditions, the cease-fire would become null and void.

In his press conference the Iraqi defense minister also admitted for the first time that, despite previous claims to the contrary, Iraqi forces were not in control of Khorramshahr, the provincial capital of Ahwaz or of the key Iranian garrison and communications city of Dezful further north. Khairallah said Iraqi forces were only on the outskirts of these cities.

Khairallah's press conference was seen as one more attempt by Iraq to seek a graceful way of disengaging from the conflict, which apparently has mired down the Iraqi Army inside Iran in a costly war of attrition, with neither side making any significant advances.

The longer the war continues, observers here believe, the more it threatens to stir up internal political dissent within Iraq as people begin questioning the government's promises of quick and easy victory.

With most of their oil industry already crippled by Iranian air strikes, the Iraqi people are beginning to face shortages of bottled cooking gas and gasoline.

The government's desire for a cease-fire, despite its insistent claims that it still has the initiative in the war, is seen as an attempt to disengage without losing face before the economic dislocations in the country stir greater opposition to the regime.

The government clearly was eager to give the impression to the Iraqi people that things were indeed returning to normal despite the war.For the first time in two weeks of all-night wartime blackouts throughout the country, the government ordered the lights turned on in villages and cities today.

In Basra, a rivedr port city of potholed streets and crumbling buildings, street lights blazed into the night tonight, restoring a semblance of normality. Street lights had been turned out at night since the war began Sept. 22. Coffee shops along the city's central canal were crowded, juice stores along the streets were doing a booming business, and even a barber shop remained open long after dinnertime.

In another small sign of the government's desire to show that all is well, the constant fare of television propaganda about the war was broken this evening by a program of Popeye cartoons.

In announcing its resumption of hostilities, the Iraqi Revolutionary Command Council, the country's top executive body, said this evening that it had been forced to continue the fighting because of Iran's "irresponsibility and aggression" in refusing to honor the cease-fire.

"Therefore Iraq has resolved to continue its honorable battle no matter how long it lasts and how costly it is," the council's statement said. "Our armed forces will teach the Persians a lesson. With the help of God, our armed forces will continue their advance."

In Tehran, the official radio said the Soviet ambassador to Iran, Vladimir Vinogradov, told Prime Minister Rajai that Moscow and Tehran hold a "common view" on foreign policies and offered Soviet military aid.

"We can cooperate in various fields and are prepared to help you with military equipment," the radio quoted the envoy as saying. However, Rajai reportedly refused the offer, complaining about past Soviet actions including its military aid to Iraq and its invasion of Afghanistan.

In response to Iraqi claims that its warplanes bombed Tehran's airport and three other targets in retaliation for an Iranian air raid on Baghdad at dawn, Iran's military command said that most of the attacking Iraqi Migs had been shot down. The command acknowledged that Iraqi planes attacked the Tehran airport, the northwestern city of Tabriz, Kermanshah and Piranshahr in the west and the Kharg Island oil terminal in the Persian Gulf.