An international peace conference backed by Poland's communist authorities opened here today as authorities detained three opposition leaders and broke up a press conference in an effort to silence criticism of an event that has divided intellectuals in Poland and abroad.

As about 350 delegates from 47 nations gathered for the nominally private Congress of Intellectuals for a Peaceful Future of the World, police detained dissident Jacek Kuron and former Solidarity trade union spokesman Janusz Onyszkiewicz in their homes, their families said.

The two activists had planned to meet journalists and conference delegates to report on Polish political prisoners and the recent dismissal of 70 rectors and deans from universities. They were taken to the Interior Ministry, nominally for questioning, and after being released tonight, they were ordered to report again on Friday, family members said.

Later, police interrupted a press conference in Kuron's home attended by several other opposition intellectuals, a group of western reporters and two Austrian delegates to the peace conference. Barbara Malak, a psychologist at Warsaw University who spoke at the meeting, was detained.

The police actions and controls over debates at the congress drew protests from western delegates and threatened to mar an event that has become a focus of propaganda for the government of Gen. Wojciech Jaruzelski. Although the congress is billed as an independent initiative of Polish intellectuals, authorities have given it heavy publicity in state media and delegated high officials to speak at its sessions.

Jaruzelski's government has sought recently to bolster its international image and break a four-year deadlock in relations with western countries, arguing that the country's political situation has "normalized" since the suppression of Solidarity in 1981. Conference organizers sought to persuade scores of prominent western artists and intellectuals to attend the four-day congress.

Today's opening, however, showed that the Warsaw meeting had failed to attract significant western participation and underlined the government's continuing difficulty in controlling Poland's opposition-dominated intellectual community.

A substantial majority of the 192 foreign delegates named by congress officials today were from Communist countries, while many of the remaining representatives from Latin America and Western Europe were drawn from Communist parties or leftist movements. The 11 U.S. delegates who had arrived by this morning included three Marxist philosophers, the rector of the University of Bridgeport (Conn.) and representatives of several religious groups.

"We were open to everyone," said Marian Podkowinski, a foreign affairs writer for the government newspaper Rzeczpospolita and a congress organizer. "But a lot of people won't come because they don't like Poland or don't like the regime here. No congress can have everyone."

Many Polish intellectuals with international reputations, such as writers Stanislaw Lem and Tadeusz Konwicki, composer Krzysztof Penderecki, poet Zbigniew Herbert and film maker Andrzej Wajda were excluded or refused to join the 124-member Polish delegation. Instead, the delegation is composed primarily of activists of communist or progovernment political movements and members of official cultural organizations.

In interviews and statements before the congress, Polish delegates who will lead the discussions have promised an open exchange of views but have emphasized such Soviet Bloc themes as preventing the development of space-based weapons. Today's inaugural session opened with a speech by the speaker of the legislature, Roman Malinowski, praising Soviet arms policies followed by the reading of a message from Soviet leader Mikhail Gorbachev.

Polish officials said they took various steps before the congress to head off controversy over the government's internal policies. Bogdan Suchodolski, the head of the organizing committee, said in an interview that he had intervened with court authorities to obtain the postponement of a Supreme Court hearing of the case of imprisoned Solidarity activists that was scheduled to take place this week.

Nevertheless, several European delegates said today that they intended to raise the issues of Polish political prisoners and the university dismissals at the congress.

Several opposition organizations issued statements seeking to draw the attention of the congress to Poland's political prisoners.