British and Argentine forces were reported to have clashed at defense lines west of Stanley yesterday as the long-awaited ground battle for the Falklands' capital began.

The Defense Ministry in London said British soldiers closing in on the entrenched military garrison at Stanley attacked Argentine troops at Mount Kent, a 1,500-foot hill about 12 miles from the capital. The hill is believed to be heavily fortified with artillery and is considered the first line of defense for the estimated 7,000-man garrison.

The ministry also reported that British Harrier jets again had attacked Stanley's airfield and military installations. It gave no report of casualties.

Britain's Press Association news agency said there were unconfirmed reports that the British had also attacked Two Sisters ridge farther to the east and that more than 3,000 troops from the requisitioned cruise liner Queen Elizabeth 2 had been ferried ashore near Stanley in Royal Navy assault boats.

Meanwhile, Argentina continued to insist that its warplanes had inflicted serious damage on a British aircraft carrier Sunday. Air Force chief Basilio Lami Dozo, a member of Argentina's ruling military junta, said pilots "saw a mass of smoke, flames and explosions" from the carrier, which he said he could not identify. News accounts in Buenos Aires identified the carrier as the Invincible.

The British Defense Ministry denied again yesterday that any of its ships had been hit in Sunday's Argentine air raid. A ministry spokesman added, "We have no information about a second landing." Argentina also had no immediate comment on the reports.

British correspondents with the fleet reported that British frigates may have destroyed two Exocet missiles fired by Argentine Super Etendard warplanes and may have shot down one of the Etendards. The report, if confirmed, would constitute the first British claims to have successfully countered the Exocet and to have downed an Etendard. The French-built Exocet has already sunk two British vessels.

Three battalions of Royal Marines and a battalion of paratroopers have crossed East Falkland Island toward Stanley along a northern route from San Carlos, where British forces first landed 11 days ago. The forces, the northern arm of a two-pronged advance, reportedly captured without resistance the settlements of Douglas and Teal Inlet on Sunday.

Yorkshire Post correspondent Derek Hudson said in a dispatch from Teal Inlet that the British troops "forded two rivers, waist-high in freezing conditions, splashed through dozens of streams and trudged through strength-sapping marshes."

Lt. Col. Hew Pike, commander of the paratroopers, told Reuter reporter Leslie Dowd at Teal Inlet: "We're halfway there and the men are spoiling for a fight and raring to get stuck in."

To the south, another paratrooper battalion has crossed East Falkland along an unpaved clay track from the twin settlements of Goose Green and Darwin, which were captured Saturday after fierce fighting. Britain said 1,400 Argentine prisoners were taken.

London, updating its casualty figures, said yesterday that 17 men had been killed in that assault. Argentine casualties were said to be significantly higher. London also reported that the cargo vessel Atlantic Conveyer, damaged by Argentine warplanes more than a week ago, had sunk.

In what appeared to represent a significant shift in Argentine foreign policy, Foreign Minister Nicanor Costa Mendez announced that he would travel to Havana to attend a meeting of foreign ministers of nonaligned nations Wednesday.

Argentina has been a member of the nonaligned movement since 1974 but has never been represented at a nonaligned meeting by a member of the Cabinet, according to officials in Buenos Aires.

Before the onset of the conflict with Britain, the government of President Leopoldo Galtieri was considering reducing its involvement with the nonaligned movement or even withdrawing from it because of its ties with Cuba and perceived inclination toward the Soviet Bloc. Foreign Ministry officials said that Costa Mendez intended to appeal to the nonaligned ministers for their support in the South Atlantic conflict.

Both Costa Mendez and the Air Force's Lami Dozo also said that Argentina was holding discussions with several Latin American countries on obtaining military aid. Peru, Venezuela and Bolivia have indicated they would provide arms to Argentina under certain conditions.

Lami Dozo was also quoted as telling reporters that arms purchases by Argentina from the Soviet Bloc "could be studied if the hostilities countinue." The remark was the most explicit warning so far by a junta member that Argenina might seek arms outside the West.

After a half-hour meeting with Galtieri, Soviet Ambassador to Argentina Sergei Striganov refused to comment on whether the Soviet Union was willing to provide material aid to Argentina. He told reporters, "We are already supporting Argentina diplomatically, politically, in the Security Council, in the media and here in Buenos Aires."

Former British foreign minister David Owen, a leader of the opposition Social Democratic Party, flew to New York on an unofficial mission to see U.N. Secretary General Javier Perez de Cuellar to determine whether there was any prospect of securing an Argentine military withdrawal from the Falklands in a way that would be less humiliating than total surrender.

One of the British dead at Goose Green, Lt. Col. Herbert Jones, commander of the 2nd Battalion of the Parachute Regiment, was hailed as a hero in the British press yesterday. Some newspapers said he should be awarded the Victoria Cross, the nation's highest military honor.

Prince Charles was among many who sent condolence messages to Jones' widow, Sara. "If he had to die, then I believe he would have liked to have died the way he did," she told reporters. "He died as he lived--a soldier."

British reporters with the task force said Argentina used different but unsuccessful methods to attack by air at night. Until Sunday Argentine air raids had been limited to daylight hours.

They said aging British-made Canberra bombers carried out high-level raids against the fleet Sunday night and that a C130 Hercules crew dropped bombs by shoving them out of a cargo door. In both cases, the reporters said, no damage was done.

Britain has begun to move some of the 1,400 prisoners taken at Goose Green to San Carlos where they have been put aboard a task force ship.

Press Association correspondent Richard Savill reported from the task force that hundreds of the prisoners, many of them teen-agers, looked frightened and bewildered as they were marched from helicopters down to the ship's hold. Their boots were muddy, their faces unshaven, and they clutched damp sleeping bags, tents and blankets, according to Savill.

Once inside the hold, Argentines were sat down and crouched in rows with their hands behind their heads.

One by one they were stripped, searched and documented, according to the provisions of the Geneva Convention on prisoners of war, Savill reported. Personal possessions and items that could inflict self-injury were removed. They were given a set of clothes and each prisoner was numbered and labeled according to his rank.

Savill said the men looked thin and one prisoner's rib cage clearly protruded. One of them told a British officer he had only eaten a bowl of rice in two days.

In Buenos Aires, the Argentine military command offered no official report on the military situation in East Falkland Island. The military joint chiefs of staff reported, however, that Argentine bombers carried out raids Sunday night and early yesterday morning against British bases at San Carlos, Darwin and the Goose Green airstrip.

Although attention in Buenos Aires was dominated by what was described as an unprecedented victory over Britain's South Atlantic task force, Argentine officials continued to lay the public groundwork for a possible military defeat.

Defense Minister Amadeo Frugoli said in a radio broadcast that Argentine troops were continuing to fight "in unfavorable conditions," saying the forces facing the advancing British ground troops were greatly outnumbered.

"I would say that Argentina has achieved victory by demonstrating that a country that exercises its rights of sovereignty can count on the support of an entire continent and many other countries," Frugoli said. "And by having changed the situation of colonialism and injustice, Argentina has already won political objectives that make it victorious."

The Argentine military command is said to believe that British forces can be weakened so that they will not be able to storm the defenses at Stanley and will be forced to retreat, opening the way for a cease-fire that would preserve Argentina's position on the Falklands.

Military officials offered a detailed account yesterday of the attack by Argentine planes on the Invincible.

The carrier was said to have been hit by an Exocet and by at least two 500-pound bombs. The military command said Sunday that two A4 Skyhawk warplanes were shot down in the operation.

Buenos Aires newspapers reported the military's account of the attack with banner headlines, but skepticism seemed to be growing by late yesterday. Several newspapers published dispatches from London carrying the British denials and reporting advances by British troops toward Stanley.