British commandos have launched attacks on the outer ring of defenses of the Argentine garrison around the Falkland Islands' capital of Stanley, British correspondents with the advancing troops reported in dispatches reaching here today.

Royal Marine commandos were airlifted by helicopter Wednesday from British forward bases on Mount Kent, 10 miles west of Stanley, to within five miles of the town, according to the censored and delayed pool dispatches from reporters on the scene. They said the commandos had begun Wednesday night to probe and attack Argentine front-line positions.

"By the time this dispatch reaches London," reported Sunday Telegraph correspondent Charles Laurence, "the British assault forces will be on the ring of hills surrounding the estimated 8,000 Argentines in the Stanley garrison." Laurence quoted a senior commanding officer as telling officers of the commandos, "It now looks as if we shall soon be in contact with the enemy."

Maintaining a four-day-old official news blackout on the beginning of the climactic assault on Stanley, the British Defense Ministry would not comment on the dispatches, which were sent here via military communications and cleared by the ministry.

However, a senior military source said the action described in the reports would be the next expected step after establishment of the British forward line on the high ridge commanded by Mount Kent. Once the hills nearer to Stanley have been captured, he said, British commanders would have several options for retaking the capital.

The news blackout here is designed to keep the Argentine defenders guessing about those options, including possible landings from the sea, the source said. He noted that nothing has been said publicly about the more than 3,000 Welsh and Scots Guards and Gurkhas who were reportedly transferred from the luxury liner Queen Elizabeth 2 to landing craft in the South Atlantic several days ago.

Other sources suggested these troops already have been landed at the original British beachhead at San Carlos, about 50 miles west of Stanley. Their reinforcement of the British ground base there would free any troops remaining from the original landing group of 4,000 to 5,000 Marines, paratroopers and support troops to cross East Falkland Island for the final assault.

Argentine reports that the Stanley garrison had been reinforced this week with as many as 2,000 troops flown in from the mainland were dismissed by officials in London. "That's what we call Invincible information," said one source, referring to repeated Argentine media claims that the British aircraft carrier Invincible has been hit or sunk.

In dispatches reaching London today, the British correspondents described how the commandos they accompanied had flown by helicopter from San Carlos to the Mount Kent forward base. Larger forces of Marines and paratroopers have been advancing to the base on the ground after capturing Darwin and Goose Green to the south and Douglas and Teal Inlet settlements to the north.

Military sources here said British operations likely would begin with observation and reconnaissance forays of Argentine positions around Stanley, followed by shelling from both land artillery and warships in the British task force. The commandos' task subsequently would be to pinpoint and attack Argentine front-line posts on the hills between Mount Kent and the capital. Under one potential plan of attack, the main British forces could then move up behind the commandos, the sources said.

"The mission is to harass and probe enemy positions until we know his exact strength and whereabouts. I am not going to blunder into a hornet's nest for lack of preparation," the senior commanding officer of the Marine commandos was quoted as telling other officers during a Wednesday night briefing at an undisclosed staging area five miles from Stanley.

"When we are sure, we will go forward and take out those positions," he said, according to a dispatch from Glasgow Herald correspondent Ian Bruce. "The men will move into action in basic fighting order, carrying bullets, beans and water. Packs will follow later. Be prepared for enemy artillery bombardment."

Dispatches from the correspondents reported steady movement of men and equipment by ground and air toward the British-occupied high ground west of Stanley. The foggy, cold and wet weather now prevailing in the Falklands was described here as both an asset and a liability for the British.

"It helps because it enables things to be done under cloud cover," said one military source. There have been no reported attacks by mainland-based Argentine warplanes on the British forces for days.

"But it can also hurt," the source added, "if the cloud cover is so low that it hampers helicopter movement." He noted that the rain, cold and snow is uncomfortable for troops on both sides.

Senior Defense Ministry officials said here today that they did not expect the Argentine forces to surrender without at least some fighting. They said about 250 Falklands residents are believed to be still in Stanley.

Much of East Falkland now appears to be under effective British control, and officials here say about 200 Argentine stragglers have surrendered in recent days to the British forces who captured Darwin and Goose Green nearly a week ago. The number of Argentine prisoners taken there has grown to more than 1,600, according to these officials.

Defense officials in London said they still were concerned that Argentina might try again to attack a major British target away from Stanley. They cited Britain's two carriers and the main British ground base at San Carlos as potential targets of an all-out air strike or the German-built Argentine submarine still believed to be lurking around the Falklands.

The Argentine garrison around Stanley was still well-armed with heavy artillery and antiaircraft weaponry, officials here said. But they believed that the Argentine forces had few helicopters or usable planes left at Stanley.

In a confidential briefing today for British defense correspondents, a senior Defense Ministry official also expressed concern that Argentina may be obtaining sophisticated replacement weapons, including air-to-sea missiles that could menace British ships, from countries the official refused to identify. The official said the weaponry obtained may include antiship missiles that could be fired by Argentina's Mirage fighter-bombers.

The official said this could enable Argentina to continue dangerous hit-and-run air attacks on British ships even after the Falklands are recaptured