The Swiss government today ordered the closure of a bureau of the Soviet news agency Novosti, charging that it had served as a "center for subversion" by helping train youthful antinuclear and peace activists.

Switzerland ordered the director of Novosti's office in the Swiss capital of Bern to leave the country, becoming the seventh western nation recently to expel Soviet officials on allegations of espionage or other interference. Justice Ministry spokesman Ulrich Hubacher said that the action was not connected to the recent expulsions of alleged Soviet spies from the United States, France, Britain and Australia. Italy and Spain also have expelled Soviet officials.

A government statement alleged that the Bern bureau had been used as a center for the "political and ideological indoctrination" of young members of the Swiss peace and antinuclear movements and for planning street demonstrations including an attempt to disrupt a Swiss parliamentary debate last July.

Swiss authorities said young members of the Swiss peace movement had met frequently at the Novosti office and then were sent to train other youths, "even to the point of paramilitary exercises."

The Swiss Federal Council, part of the executive branch, warned in a note to the Soviet Embassy that it will "act resolutely and with all means" against further interference in Switzerland's domestic affairs.

Alexei Dumov, director of the agency's office, was ordered to leave Switzerland by May 8. Dumov, described as being in his mid-fifties, had been Novosti's chief correspondent in Switzerland since 1978.

In an unusually forceful and explicit statement issued this morning, the Swiss authorities charged that the Novosti bureau in Bern had "served as a center for disinformation, subversion and agitation" rather than as a news agency.

Two full-time Swiss employes at the Novosti bureau allegedly made contacts in the Swiss youth movement. The employes were questioned by police but so far have not been arrested or charged.

The Swiss government's allegations have been interpreted here as an attempt to show a link between the Soviet intelligence service KGB and the youth riots that rocked Swiss cities in 1981.

The riots, principally in the cities of Zurich, Bern and Lausanne, caused millions of dollars of damage to property and tarnished Switzerland's world image as an island of order and stability.

Swiss authorities also alleged that the Novosti bureau had engaged in widespread disinformation activities. They said that these had included an attempt to link the Swiss intelligence services to the suicide in Switzerland in 1980 of a Soviet employe of the International Cocoa Organization.

The Swiss government's statement made clear that it considered the Novosti office in Bern to be a front for the KGB but underscored that Novosti had not been involved in espionage activities. The agency's one-man Geneva bureau was not affected by the closure order.

"Activities at Novosti in Bern did not involve espionage but efforts to influence and subvert public opinion in Switzerland," Justice Ministry spokesman Hubacher said.

In a separate statement, the Swiss Federal Council said Novosti's activities in Bern "violated Swiss sovereignty" and disrupted relations with other countries. "In the long term they endangered the internal and external security of our country," the council said.