West Germany expelled two Libyan diplomats today as U.S. officials stepped up pressure on Bonn to take greater diplomatic and economic reprisals against Muammar Qaddafi's government, which they say helped plan the bombing at a West Berlin discotheque last weekend.

Government spokesman Friedhelm Ost announced the expulsions in a press conference here. Ost said that West Germany had gathered "indications" from "various sources" that the Libyan "People's Bureau," or embassy, in East Berlin, the capital of communist East Germany, was involved in Saturday's explosion. But he added that Bonn still lacks "concrete evidence" implicating Libyans in the actual planting of the bomb, which killed a U.S. soldier and a Turkish woman and injured 204 others, including 64 Americans.

The expulsions were not linked to the bombing, according to Ost, but came because the two Libyans were engaged in "impermissible activities," a term usually used to indicate spying.

As West German officials explain it, the evidence indicates that the Libyans in East Berlin were involved in planning the attack, but there is said to be no evidence yet that Libyans in West Germany were involved. Because Libyans assigned to the Bonn embassy engage in other "impermissible" activities, they can be expelled on other grounds.

Today's expulsion, Bonn officials said, was ordered in part to placate Washington, which has been pressing the West Germans for action. The Reagan administration is known to want Bonn to shut down the entire Libyan diplomatic mission here. But West German officials indicated that this was unlikely barring further developments.

West German sources said there was a high state of alert, however, for fear of other attacks on Americans in Germany and elsewhere in Western Europe.

In another development, American, British and French military authorities were reported seeking to restrict the entry of Libyans into West Berlin from East Berlin. Such a move would be carried out under the postwar authority of the allied powers in the divided city.

The United States welcomed today's action, a spokesman at the American Embassy here said, but suggested that further actions against Libya are expected. U.S. and West German officials are continuing with "intense consultations to see that all steps are taken to ensure full protection and security of American personnel and installations," the spokesman said.

The expulsions came a day after the United States presented senior West German officials with its evidence that Libya had helped organize the bomb blast and asked Bonn to launch reprisals against Qaddafi, a government official said today.

The evidence included references to radio traffic between Tripoli and East Berlin about the bombing, the official said. He declined to elaborate.

The West German Cabinet discussed the U.S. request in a meeting today and the expulsions were announced after the meeting, a government official said.

The chief of the Libyan embassy here was summoned to the Foreign Ministry this morning and informed that the two diplomats were being expelled, Ost told journalists.

The two were identified as middle-ranking diplomats Ahmed Omar Issa and Mahmud Ahmed Shibani, according to West German security sources. They had been under observation "for a long time," Ost said. Their departure will reduce the Libyan embassy staff here to nine.

Diplomatic sources here said they consider the expulsions unusual because the investigation in progress on the West Berlin bombing has not concluded that Libyans were directly involved in it.

The move not only threatens Bonn's ties with Tripoli, the diplomats said, but also the links between Bonn and East Berlin at a sensitive time.

East German leader Erich Honecker is expected to make a final decision soon on his long-awaited trip to West Germany. When Honecker meets with Soviet leader Mikhail Gorbachev at the Communist Party congress in East Berlin next week, the two are expected to discuss the trip.

"Any bad vibrations could tip the balance against it," one western diplomat here said.

West German Chancellor Helmut Kohl held long-scheduled talks with East German Politburo member Gunter Mittag in Bonn today, but officials declined to say whether they discussed the bombing.

The East German government denied any connection with the bombing in a statement released today by the Foreign Ministry in East Berlin.

The statement, carried by the East German news agency ADN, expressed "disgust and indignation" over the attack. It said the Foreign Ministry "resolutely rejects attempts to associate the GDR [East Germany] with this criminal act. The hope is expressed that such criminal operations will not be used to poison the international atmosphere." The statement was issued after West Germany's Bild newspaper named a diplomat in Libya's embassy in East Berlin as a prime suspect in the discotheque bombing