Argentina charged today that British fighter planes attacked and sank an Argentine fishing boat 66 miles south of Stanley on the Falkland Islands, then strafed survivors who attempted to take to sea in lifeboats.

The military command called the alleged action "a perfidy unknown until now in the history of war in the sea." A naval spokesman said all members of the crew, reported to number 35, were presumed to have died.

In London, the British Defense Ministry announced it had attacked and captured the boat, which it said was suspected of spying, but rejected as "ludicrous" the charge that survivors had been strafed. Britain said one crewman died and about two dozen were captured including 13 injured.

The military command here said the attack on the Narval came hours after Argentine forces at Stanley and Darwin on the Falklands repulsed an attack by British boats and helicopters after a 50-minute battle early this morning.

The military's joint chiefs of staff offered no details on the attacks on the islands, which it said began at 12:40 a.m. EDT. The private news agency Noticias Argentinas quoted a military official on the Falklands, Maj. Gonzalez Iturbe, as saying in a telephone interview there were no Argentine casualties.

Argentina's account of the attacks came as Foreign Minister Nicanor Costa Mendez and other high-ranking officials reiterated Argentina's willingness to negotiate with Britain in the United Nations but continued to say that Argentina must have assurances of sovereignty over the disputed South Atlantic islands in any settlement.

The military command said "energetic denunciations" would be made of the fishing boat sinking before the United Nations and other "international forums." It accused Britain of violating "the most elemental humanitarian rules and the traditional standards of rescue at sea."

The fishing boat was attacked by a British Sea Harrier shortly after 8 a.m. EDT within the 200-mile exclusion zone established by Britain around the Falklands, the Argentine military command said. Argentine officials offered no explanation for the boat's presence in the zone, where Britain has threatened to attack all Argentine vessels.

A communique released here reported four radio calls made by the captain of the boat, which apparently formed the basis for Argentina's charges. The captain was first quoted as saying that he was being attacked by one plane and that there were badly wounded men on board.

Shortly afterward, the captain radioed that "the fishing boat is sinking; we have 30 minutes left afloat; we have launched an orange boat with the seriously wounded," according to the communique.

The captain then radioed minutes later that 25 men were abandoning the boat. The communique said the captain then reported, "One of the wounded died. Another English plane flew over us, attacking, and destroyed the life raft. There is one boat left for those who remain. We need help urgently."

Finally, according to the communique, the boat captain radioed, "They are sinking the boat that was left. We are throwing ourselves into the sea. Long live the Fatherland."

The military command later said that a rescue boat painted red had been dispatched from the Falklands to look for survivors. The Foreign Ministry said Argentina had appealed to Japanese, Polish and Soviet fishing boats in the area for help.

A naval spokesman said, however, that sailors in the freezing water would not be expected to survive more than 10 minutes and that it was presumed the crew of the boat was dead.

With military action resuming in the South Atlantic after a 4 1/2-day lull, Argentine Foreign Minister Costa Mendez said in a television interview that "sovereignty is not a precondition" for the onset of negotiations with Britain.

But, in the interview on "Face the Nation" (CBS, WDVM) filmed in Buenos Aires, Costa Mendez added, "We are seeking as our goal sovereignty" over the Falklands and their dependencies, the South Georgia and South Sandwich Islands. "There is no other goal but sovereignty," he said.

The minister's statement did not appear to depart from previous Argentine positions on an accord with Britain. Argentina has offered in the past to set aside explicit recognition by Britain of its claim as long as it obtains at least implicit assurances that the talks will lead to recognition of its sovereignty.

The Foreign Ministry issued a clarifying statement to that effect this afternoon. It said that Costa Mendez's statement meant that "all negotiations should lead inexorably to the recognition of Argentine sovereignty."

During earlier negotiations with U.S. Secretary of State Alexander M. Haig Jr., Argentina indicated that in the absence of a direct recognition of sovereignty, the government here would have to have a superior role in the temporary administration proposed in the Falklands or a fixed date for the end of negotiations, after which territorial control automatically would be ceded to Argentina in the absence of an agreement.

In Washington, the State Department did not treat Costa Mendez's remarks as a breakthrough in the diplomatic impasse. The department issued no public statement on the minister's remarks, but initial comments of U.S. officials were guarded and skeptical. They noted that the minister's description of the Argentine position appeared to contain contradictions, and they said they were looking to the discussions at the United Nations for concrete signs of whether the Argentine position had changed substantially.

The U.N. proposals by Secretary General Javier Perez de Cuellar do not mention sovereignty, but, according to Argentine sources, include a beginning and ending date for negotiations.

With continued military action expected in the Falklands, Buenos Aires remained tense today. Rumors continued to sweep the capital, and hundreds of riot police arrived at the U.S. Embassy yesterday morning after reports that a demonstration would take place.

No demonstration materialized, but two bomb threats and several obscene phone calls came into the embassy switchboard, embassy sources said.