Undated (AP) _ NEW DELHI, India (AP) - Indian newspapers said today that a Soviet citizen, an East German diplomat and a Polish diplomat have been expelled in connection with an investigation into an alleged spy ring.

The Express, India's largest circulation daily, said a ''Soviet national attached to the USSR Embassy in New Delhi'' was expelled. It did not identify the person.

''Intelligence sources said that another Soviet official may be involved in the espionage business,'' the newspaper said.

The Express and other major newspapers also reported that the Polish and East German diplomats had been expelled in connection with a continuing investigation into alleged spying activities. Nearly 20 people have been arrested in recent weeks on suspicion of spying.

Vladimir N. Tsatsyne, a spokesman for the Soviet Embassy, told The Associated Press: ''There are no grounds whatsoever behind the allegations of Soviet involvement made in a section of the Indian press.''

A man who answered the telephone at the Polish Embassy and East German press attache Rolf Lais each said they had no comment on the news report. Poland's ambassador to India, Ryszard Fijalkowski, has called the allegations of his embassy's involvement ''baseless.''

India's External Affairs Ministry spokesman, Salman Haidar, would neither confirm nor deny the reported expulsions. ''The government is investigating and taking appropriate action,'' he said.

The Express said the Soviet was expelled following ''confessions'' by Ashok Jaitkha, a businessman arrested in connection with the espionage case. Jaitkha, operator of a hosiery company in the city of Ludhiana in Punjab, is reported to have had extensive business dealings with Eastern Bloc countries.

A senior court official said Monday that Coomar Narain, a New Delhi businessman suspected of being a key figure in the spy ring, told a magistrate that he sold military, industrial and political secrets to diplomats from East Germany, Poland and France.

The court official quoted Narain as saying he worked in espionage for the past 25 years, and that he sold copies of classified documents to diplomats in return for their help in winning foreign contracts for his company.

Narain's employer, Yogesh Maneklal, was arrested Tuesday in the Western port city of Bombay following Narain's court statement.

The French deputy military attache, Col. Alain Bolley, was called back to Paris on Jan. 20 amid allegations that he was involved in espionage. He denied the allegations. The French ambassador, Serge Boidevaix, also is being recalled, but France has not said it had anything to do with the spying case.

Narain reportedly identified a Polish contact as Jan Haberka, who returned to Warsaw last August after serving as a deputy commercial attache for four years.

The allegations of Polish involvement came only days before the scheduled Feb. 11-15 visit by Polish leader Gen. Wojciech Jaruzelski. The Indian and Polish governments said Tuesday that Jaruzelski still plans to visit India.