Military authorities expelled 35 foreign newsmen from East Pakistan yesterday after confining them to a hotel in Dacca for more than 48 hours.

Soldiers of the Pakistani Army threatened to shoot the newsmen if they left the Intercontinental Hotel in North Dacca, from which they could see troops firing on unarmed civilians who supported the East Pakistani rebels.

Before they were put on a plane to Karachi, the newsmen, including the New York Times correspondent, Sydney H. Schanberg, were searched and their notes, films and files were confiscated.

The represented newspapers and other news media in the United States, Australia, Britain, Canada, France, Japan and Russia.

While in Dacca, the newsmen were prevented from filing any dispatches or contacting diplomatic missions.

Correspondents for The Associated Press and Reuters apparently were not at the hotel when the other newsmen were rounded up. Offices of the two news services in New York said that they had not heard from their men in Dacca.

Mr. Schanberg reported that when the lieutenant colonel in charge of the area around the hotel was asked why the foreign press had to leave, he replied: "We don't have to explain. This is our country."

Then as he turned away smiling contemptuously, he added: "We want you to leave because it would be too dangerous for you. It will be too bloody."

A.M. Rosenthal managing editor of The Times, protested the treatment of Mr. Schanberg and the others in a telegram to the Pakistani Government.

The telegram said:

Stunned by unwarranted and unprecedented expulsion of New York Times correspondent Sydney Schanberg and more than 30 other foreign correspondents from Dacca. Contrary to all principles of international press freedom, Mr. Schanberg and others were confined to the Intercontinental Hotel in Dacca under threat that they would be shot if they left the building in performance of their journalistic duties.

"They were subsequently expelled from the country after confiscation of their papers and film. Can only believe that this must have been an error on part of military authorities. Trust that your Government will rectify this situation immediately.

The plane carrying the expelled newsmen from Dacca stopped to fuel at Colombo, Ceylon, where the correspondents for the Times, the Washington Star, Newsweek and the Baltimore Sun were able to telephone a pooled dispatch.

With the expulsion of the foreign press the main source of news on East Pakistan was the Press Trust of India, a group of Indian news agencies. Pakistan, protesting what it charged was India's "interference" in her internal affairs, asserted that the Indian news reports were exaggerated and "designed to malign Pakistan."