A Yugoslav-born American citizen who returned to Yugoslavia for his father's funeral early in April was arrested there later that month and apparently has been carged with espionage by authorities in Belgrade.

The case of Bosco Simic, 50, a associate dean of Moraine Valley Community College in Palos Hills, Ill., has attracted high-level attention within the U.S. government.

Assistant Secretary of State Lawrence S. Eagleburger, last U.S. ambassador to Yugoslavia, called on Yugoslav authorities regarding the case during a trip to Europe last month.

Sen. Charles H. Percy (R-Ill.) chairman of the Foreign Relations Committee, met here July 6 with Budimir Loncar, Yugoslavia's ambassador to this country.

Until now, the case has been handled quietly through diplomatic channels, as is normal, with U.S. consular officials visiting Simic in the Istrazni Zatvor in jail in Belgrade.

After Meeting with Loncar, Percy wrote to Simic's wife, Zlata, informing here that Loncar had said things would turn out all right for her soon.

Then information was received from lawyers in Belgrade that Simic, who had been held without charges since April 20, had been indicted July 28 under a portion of Yugoslav law that includes espionage.

After word of that indictment reached the Chicago suburb where Simic lives, friends and family decided to contact reporters, fearing that quiet diplomacy is not working.

"I don't know what 'soon' means," Zlata Simic said in a telephone interview, referring to the estimate given Percy by Loncar. "I don't know what to do now. I want to help him, not make it worse. But what does 'soon' mean to them -- one year, two years? Everybody has been very helpful, except there is no result so far."

State department officials would not comment on the situation, with sources indicating that the department has no official copy of charges against simic.

Simic has lived in the United States for 15 years. He worked for many years, until 1964, as a translator of Russian for the Yugoslav government. He then worked two years for a foreign trade bank in Belgrade. In 1966, during a vacation trip to France, he and his wife decided not to return to Yugoslavia and came to this country.

Other than on a charge of leaving Yugoslavia illegally, Zlata Simic, 45, says she does not know why Yugoslavian authorities would arrest her husband. She said he had no trouble receiving promptly a visa to see his ailing mother and dying father.

"We have lived here for 15 years now. We've been good citizens, never involved here in anti-communist activities," Zlata Simic said.

Other cases of Yugoslav-born American citizens arrested in thier native land have become politically explosive. In 1976, former U.S. ambassador Laurence Silberman publicly criticized Yugoslav authorites for the arrest on espionage charges of Laszlo Toth. Silberman then turned his anger on the State Department for failing to back his efforst sufficiently, and Toth was released after a year in jail.

Last year, Mirko Markotic, 29, was arrested during a visit to his homeland and sentenced to 11 years in jail after being charged by Yugoslav authorities with taking part in a demonstration against the Belgrade government in Chicago. He was released after seven months.