Three Croatian terrorists shot their way into the Yugoslav mission to the United Nations today, wounding a guard and then staged a ruse in which they had police believing for two hours that a woman hostage was being held behind barricaded doors.

In an almost comic opera ending to the seige, the terrorists abandoned their ploy of using a falsetto voice to deceive police, and surrendered meekly.

The police, in turn, then scattered the scores of reporters waiting outside the Fifth Ave. building by drawing their weapons in response to a report that a Yugoslav mission employee had broken out a machine gun.

Amid shouts of "get the window closed, get out of here!," camermen and reporters beat hasty retreats in every direction, while the police deftly spirited the Croatians away in squard cars.

Police never confirmed the machine gun rumor.

Police said the last-minute flurry of gun wielding and shouting was designed to prevent possible attacks on the terrorists by persons in the large crowd surrounding the mission.

The drama began shortly before 2.30 p.m. when, police said, three armed men burst into the four-story mission at Fifth Avenue and 67th Street after coolly walking past a uniformed New York City policeman standing guard outside, without arousing his suspiciouns.

Deputy Police Chief Francis McLoughlin said when the terrorists entered a foyer they shot a Yugoslav chauffeur, Radiomir Medich, 58, who was standing guard inside. Wounded in the abdomn, Medich later was reported in fair condition at Lenox Hill Hospital.

McLoughlin said the gunmen then bolted upstairs to a third-floor office, pursued by New York City Patrolman John Gavin, who heard the shot while patrolling outside on the sidewalk.

The terrorists barricaded themselves in the office, which police said was apparently empty at the time, and began throwing hundreds of leaflets into the street below. The leaflets demanded independence for Croatians, whose territory was annexed in 1918 along with that of Serbians, Slones and other South Slavs, to form the kingdom of Yugoslavia.

The terrorists hauled down a Yugoslav flag and shouted to police that they wanted some of the leaflets delivered to the U.N. Secretary General Kurt Waldheim. The police complied.

For the next two hours, members of the police department's hostage negotiating team talked to the terrorists through the barricaded door. McLoughlin said that at one point, the negotiators heard what they thought was a woman's voice, although he said it seemed that the "woman" had a gag over her mouth.

Assistant FBI Director J. Wallace LaPrade, who was at the scene, and New York Chief of Detectives John Keenan later concurred that there was no hostage in the office, and that the terrorists probably had faked a woman's voice.

"They had to surrender eventually and they did. The police negotiators convinced them the only thing to do was come out of there," LaPrade said.

In a circus-like atmosphere, hundreds of passersby and reporters crowded closer and closer to the front entrance of the small mission building, which is wedged between two luxury high-rise apartment buildings in the fashionable East side neighbourhood.

Casually clad youths riding tenspeed bicycles and one man carrying a miniature poodle shoved their way along with reporters closest to the door as rumors circulated that the gunmen were about to be led outside.

Some Yugoslac employees inside shouted, "Kill them. They'll never get justice." A police official at headquarters said later, "Somebody thought they saw 3 machine gun at the window, but we're not confirming that."

The incident was the second time in a year that Croatian nationalists have carried out a terrorist act in New York City. Last September a TWA jetliner with 86 passengers was hijacked at Kennedy Airport and taken to Paris by five Croats.