Cuban Migs attacked and sank a Bahamian patrol boat in Bahamian waters late Friday, killing four crewmen and wounding others, a government spokesman in Nassau said yesterday.

A Cuban government communique issued in Havana last night confirmed the sinking and said Cuban pilots had fired on the Bahamian vessel because they thought it was a "pirate boat."

"If the vessel we sank was acutally a Bahamian patrol boat, we are sincerely sorry for the incident," the communique added.

The 102-foot armed vessel had taken in two Cuban fishing boats on charges of poaching before the attack occurred, the Bahamian spokesman said yesterday. When the survivors made their way to a nearby island, five Cuban aircraft reportedly terrorized its inhabitants with repeated sweeps at palm-tree level.

The Cuban communique last night did not mention this aspect of the incident.

A statement issued by the Cabinet office last night said the Bahamas had sent a strong protest to Cuba. "There could be no question about the identify of the ship," the statement said.

In Washington, a State Department spokesman said: "If the facts are as stated by the Bahamian government . . . it appears to be a gross violation of international law."

The director of the Caribbean countries desk at the State Department, W. Robert Warne, was called to the operations center where he and other officials were following this latest Cuba-related issue last night.

While the islands of the Bahamas sit astride the Florida Straits, now clogged with small boats carrying Cuban refugees to Key West, Fla., the Nassau government until now had steered clear of the refugee issue.

Nassau earlier had refused landing rights to a plane engaged in the abortive Costa Rican airlift of Cubans. With Nassau's permission,m the U.S. Coast Guard reportedly entered Bahamian waters to rescue Cubans from one of the Key West sealift boats that foundered several days ago.

The Bahamian law on fishing rights is strict, and has resulted in the capture of both American and Cuban fishing boats repeatedly in the past. But until now, the boats of both countries have accepted Bahamian justice, paid their fines if convicted in the quick judicial processing and returned to their home waters.

Bahamian Prime Minister Lynden O. Pindling was in London yesterday. After an emergency meeting of his Cabinet, a Nassau official was quoted by United Press International as saying:

"We're in a very delicate position. We're not in a position to wage war with anybody."

A British naval officer, Cmdr. William Swinley, who is assigned to Nassau as chief of its defense forces, flew to the islands' southernmost airfield, on Ragged Island, nearest to the site of the sinking.

Swinley returned to Nassau, reportedly with the 16 remaining crewmen and eight Cubans from the two boats that had been commandeered.

A Bahamian official said the survivors made their way to Ragged Island in one of the Cuban boats, arriving yesterday morning with first word of the attack. The official said was believed that the Cuban fishermen alerted Cuban authorities by radio when their prsence was challenged by the Bahamian boat, the Flamingo.

The point where the Bahamians say tha attack occurred is about 35 miles north of Cuba, and about 30 miles south of Ragged Island. A coral reef at that point has been claimed without dispute by Nassau, which also claims control of waters above its share of the continental shelf. The line between Cuban andBahamian waters generally falls halfway between that small Santo Domingo Cay and Cuba.

As the news swept through Nassau, and the rest of the most populous New Province island on which it sits, rumors multiplied that planes carrying Cuban troops had landed on Ragged Island -- some 200 miles to the south.

There was no confirmaition of troop landings but a diplomatic source said he did believe a Cuban helicopter touched down breifly on Ragged 2sland as part of an attempt at intimidating the small population there.

A resident of this island quoted by Associated Press said that after the Cuban fishing boat docked, two Cuban jets, two reconnaisance planes and a helicopter began buzzing the island, terrorizing the inhabitants but harming no one.

"You have to wonder what was on those fishing boats to make the Cubans so anxious," the diplomat said.One of the two boats apparently was cast adrift as the Flamingo sank.

Nassau has diplomatic relation with Havana but neither maintains representation in the respective capitals. Relation, while not close, have been correct.

The Bahamas gained independence from Britain in 1973 but it remains in the Commonwealth. Although the population is only about 175,000, it is one of the fastest growing in the world.

There is a Cuban exile population estimated at perhaps 200, dating from the first years of Fidel Castro's revolution -- including the owners of the Bacardi rum distillery transplanted from Cuba. But Pindling's government. beset by an influx of Haitian refugees, has discouraged any suggestion of taking in more Cubans.

The islands welcome tourists but such famous exiles as the deposed shah of Iran and oustee Nicaraguan dictator Anastasio Somoza were allowed in only for limited periods.

According to Associated Press, the Bahamas Defense Force bought the Flamingo and a sister vessel, the Marlin, for $2 million each from Britain 18 months ago. The two boats were the main patrol ships for the 90,000 square miles of water surrounding the coral islands.

Other than the brief statment, the U.S. government gave no indication of the reasons for what clearly was heightened concern over the incident. Officials were in touch with the U.S. interests section in Havana, which is augmented with officers trying to sort out the refugee crisis.

U.S. officials have indicated since Castro cleared the way for the massive outflow of discontented Cubans that his actions appear quite unpredictable. Castro's moves suggest deep-seated internal difficulties beyond the country's admitted economic troubles, these officials say.