Two armed Croatians invaded the West German consulate in downtown Chicago yesterday, took eight hostages and demanded the release of a Croatian emigre leader imprisoned in Cologne, Germany.

Two of the hostages - Eva Raster, 16 year-old daughter of German Consul General Egon Raster, and a man identified only as an Austin national - were released unharmed a few hours after the invasion of the consulate on the 10th floor of a building on fashionable South Michigan Avenue.

After questioning by police and the FBI, Eva Raster left the building with her mother and, shunning waiting reporters, they were hustled away in a squad car. Her father said later that Raster described the Croatians as "very friendly."

Pia Ortleb, a secretary who was one of the remaining hostages, told a reporter by telephone shortly after the takeover. "They are very upset. It is very tense. They are threatening to shoot if I tell you anything."

Asked if one of the armed men would speak to a reporter, she replied, "They don't want to talk to anybody. They are too busy holding the hostages."

Richard Julien, a police bomb and arson investigator, said the Croatians were armed with pistols and carried two boxes that they said contained explosives. They wired one of the boxes under the desk of consulate administrative officer Werner Ickstadt, the highest ranking official among the hostages, according to Consul General Raster.

Chicago police public relations director David Mozee told reporters late yesterday afternoon that the FBI was handling negotiations for release of the remaining hostages. "We are prepared to wait them out," Mozee said. "We have plenty of time."

A team of top German officials from the embassy in Washington and the German mission at the United Nations arrived in Chicago late yesterday afternoon to take part in the negotiations. Their identities were not immediately learned.

The FBI declined to comment on the situation.

In Washington, a State Department working group headed by Anthony Quainton, the department's ambassador-level director for combating terrorism, went into action. "The United States government is following all developments closely and doing everything possible to insure the early and safe release of the hostages," a State Department spokesman said. "We regard this as a very serious international incident on our soil."

The invaders were believed to have arrived in the United States only recently from Germany.

They entered the consulate shortly after it opened at 10 a.m. (EST), asked to see the consul general, but were told by Ortleb that he was on vacation. Then they apparently pulled handguns and took the hostages.

Another secretary, whose identity was witheld, slipped away, apparently unnoticed by the armed men, and called police, who notified the FBI which set up a command post on the floor below the consulate.

Scores of local police and FBI officials entered the building and surrounding buildings, where they could see into the consulate. Several of the hostages came to the windows, waved to reporters and others in a huge crowd on the street. At one point a television reporter held up a sign saying, "Okay? Okay?" One of the hostages nodded to indicate "yes." The reporter then held up a sign saying, "Fear?" She waved her arm in a gesture that reporters could not interpret.

Consul General Raster said that the armed men demanded the release of Croatian emigre leader Stjepan Bilandzic from prison in Cologne.

Bilandzic, 39, is said to be the founder of an alleged terrorist organization called the Croatian National Resistance, whose aim is the independence of Croatia from Yugoslavia. He is charged in Germany with a 1976 attempt of the life of Vladimir Topic, the Yugoslav vice consul in Dusseldorf.

Yugoslavia wants to extradite Bilandzic to try him on charges of sending two compatriots to Yugoslavia to commit terrorist acts. Yugoslav authorities are holding four alleged terrorists whom Germany wants to extradite, pending Bilandzic's extradition.

For several weeks, Croatian nationalist leaders in Chicago - which has 120,000 residents of Croatian descent - have been picketing in front of the German consulate, distributing leaflets and contending that the extradition of Bilandzic would be tantamount to a death sentence.

Ickstadt met on Monday with five Croatian leaders and listened to their pleas, according to Raster.

The armed men in the Chicago consulate demanded to talk to Bilandzic by telephone in Cologne. The demand was granted in less than two hours. The conversation lasted several minutes.

The hostages still being held in addition to Ickstadt and Ortleb, were identified as administrative officer Peter Berndt, Martin Murmann, of the passport and visa section, and two clerical employes who are German nationals, Marlies Stulgies and Henriette Back.