The killing this month of at least 15 opponents of military rule in Suriname and the imposition of a military curfew has thrust the former Dutch colony unexpectedly into the foreground of discussions over human rights violations in the Western Hemisphere.

The deaths also touched off speculation that the left-leaning military leaders, headed by Lt. Col. Desi Bouterse, had Cuban help in their antidissident crackdown, which took place Dec. 7. The curfew was imposed at the same time.

While well-informed sources point out that there has been an increase in Cuban diplomatic activity in Suriname in recent months, they caution against drawing hasty conclusions and point out that press reports, quoting U.S. officials in Suriname, of possible Cuban involvement have not been substantiated.

Suriname's official explanation is that those who were killed were plotting to overthrow the military leadership on Christmas Day. They had been arrested, according to the official version, and were shot while attempting to escape.

Among those persons confirmed killed were the leader of Suriname's largest trade union federation, Cyrill Daal; four leading journalists and four well-known attorneys, including the chairman of the country's lawyers' association, Kenneth Gonsalvez.

"There's just no other way to describe it but as the gross and clumsy slaughter of decent people," said an American diplomat who has served in Suriname.

Once seen as one of the few bastions of democracy and civilian rule in the hemisphere, Suriname, formerly Dutch Guiana, a nation of 350,000 living in an area roughly the size of Georgia on the northeastern coast of South America, appears in danger of becoming an outcast at the same time that other nations in the region seem to be taking halting steps toward democracy.

The State Department summoned Suriname's ambassador three days after the killings and expressed in sharp terms its "indignation" at the events. In an official statement, the department said, "We are shocked by this brutality, and we deplore the lack of due process and violation of basic human and civil rights."

Secretary of State George P. Shultz, traveling in Europe at the time, expressed his "horror" at the killings, and similarly strong statements were recorded by the AFL-CIO, the International Labor Organization and the European Parliament.

The United States suspended a $1.5 million aid agreement signed Sept. 30 until there is a "satisfactory explanation" of the events. The Netherlands also suspended its payments on the 10-year, $1.5 billion aid package agreed to as part of Suriname's 1975 independence.

Dutch interests still have fairly substantial investments in Suriname, as do several North American companies. Suriname is one of the world's leading producers and exporters of bauxite, the most important aluminum ore.

Suriname was ruled by two multiparty coalitions until Feb. 25, 1980, when the government of then-prime minister Henck Arron was overthrown by a group of sergeants upset at the government's refusal to recognize their trade union.

Since the military takeover, there have been a series of power struggles and reported attempted coups, but the main power continued to be wielded by Bouterse, one of the leaders of the original sergeants' group. Bouterse heads an advisory council that appoints a civilian prime minister and Cabinet, as well as a ceremonial president.

The events of Dec. 7 are still unclear. According to some accounts reaching Washington, the alleged plotters were being taken by bus to Fort Zeelandia near downtown Paramaribo, the capital, where they were to be detained, when they apparently were gunned down.

Witnesses quoted in wire service accounts and by Radio Netherlands, monitored here, claim that the victims' wounds were too accurate to have been inflicted while the men allegedly were running away.

State Department officials said that they had received reports that 15 bodies were displayed publicly and that several appeared to have been physically abused.

The military has accused foreign interests, chiefly Dutch and American, of being behind the alleged plot against the government. No concrete evidence has been produced by the government to support its charges of a plot except a recorded statement that was broadcast by two of the slain journalists, supposedly confessing their intention to stage a coup. Several sources have suggested that the statements may have been made under duress.

The Cuban question has recurred repeatedly since the 1980 coup in Suriname, but after the appointment of a full-time Cuban ambassador in September -- one month after the Soviet Union sent an ambassador ta Paramaribo -- the issue has become more controversial.

The Cubans initiated a number of cultural and sports exchanges, and several members of the military have made trips to Havana.

Beyond this, however, any evidence of Cuban involvement in the country has been in the realm of rumor and circumstantial evidence.

The Associated Press quoted American sources in Paramaribo as saying Cuban intelligence operatives have been busy in the Surinamese capital since the ambassador, Osvaldo Oscar Carbenas, took up residence there.

Carbenas is head of the Caribbean-Central American section of the Cuban Communist Party.

Wayne Smith, former head of the U.S. Interests Section in Havana, said that while the Cubans would be interested in seeing a revolutionary government in Suriname, they more likely would look on what is happening there as "infantile extremism," and that Havana is too cautious to get tangled up in such a situation.

"We have to have the hard facts" before accusing the Cubans, Smith said.

"Whatever has happened in Suriname," he added, "is a shame and a human tragedy, with a small group of people trying to grab power and impose their will on a country."