MOSCOW, JULY 7 -- Nearly half of the members of the Communist Party Politburo were subjected today to tough questioning by delegates to the party's 28th Congress before President Mikhail Gorbachev, fearful that the session would turn into a Stalin-era inquisition, persuaded the gathering to stop evaluating the leadership individually.

Yegor Ligachev, leader of the party's conservative faction, and four allies of Gorbachev were summoned one by one before the largely conservative delegates to face questions -- many of them pointed and hostile -- about their tenure in office.

Ligachev, for example, was assailed by some liberal delegates for his alleged roles in the April 1989 street massacre in the capital of Soviet Georgia, a corruption scandal in Uzbekistan and other controversies. Some conservatives attacked Gorbachev ally Vadim Medvedev, the Politburo member in charge of ideology, who said he is prepared to step down from the ruling body to a lower office.

By late afternoon, the atmosphere in the crowded Palace of Congresses, the hall inside the Kremlin where the congress is being held, became so agitated that Gorbachev appealed to delegates to cut the questioning short.

After five of the 11 full members of the Politburo had answered questions, Gorbachev called for a vote on whether to continue, saying he had received notes from several members who objected to the process.

"If you want to bury the party, to split the party, then continue on this way," Gorbachev warned, adding, "Think hard, think hard." The congress, which had earlier voted to consider each Politburo member individually, reversed itself and agreed to evaluate the policy-making Central Committee, which includes the Politburo, in a single vote.

The day of grilling seemed to prepare the way for the ouster of a majority of the members of the Politburo, the party's highest body, at the end of the congress, although it is unclear who would replace them. The party is exploring the idea of restructuring the Politburo to include representatives from each of the Soviet Union's 15 republics, several delegates said today.

As the gathering of 4,600 Communist delegates ended its first week, a mood of discontent set in across the elegant Palace of Congresses. The congress is being held as the party is becoming increasingly unpopular across the country and as Gorbachev continues to transfer administrative power from the party to the government.

Coming on the heels of the collapse of Communist regimes in nearly all its allied countries across Eastern Europe, the Soviet party is faced with bearing the standard for communism in Europe. But so far, in six of 10 scheduled days of meetings, few speakers seemed to have addressed the changes implied in that role.

"Hardly anyone has raised the important questions," said delegate Vladimir Lysenko, "about what the party should do to reform itself or what its new position is in a multi-party system where it will not be the only party." Lysenko is one of the leaders of the Democratic Platform, a small group of delegates which has threatened to leave the party if it does not agree to more radical changes.

It is expected that many individuals brought into the party leadership under Gorbachev will be removed. Along with Medvedev, Politburo member Alexander Yakovlev has said he would be willing to quit the body. Two other full Politburo members already have submitted their resignations.

Medvedev has been the object of verbal attacks during the congress. Most have come from conservatives, who charge that he has inadequately prepared the country for understanding the reforms.

In an hour of questioning, delegates charged Ligachev with misdeeds ranging from undercutting Gorbachev's perestroika reforms to misquoting Leninist doctrine to support his own aims. One delegate charged Ligachev with instigating a decision to send troops to quell a demonstration in Tbilisi, the capital of the Soviet republic of Georgia, in April 1989. Protesters were beaten and gassed and 20 died.

Another delegate from Uzbekistan grabbed a microphone and grilled Ligachev about his alleged involvement in a bribery scandal in Uzbekistan.

The combative Ligachev, who is popular among hard-liners and is expected to survive the personnel shuffles anticipated at the end of the congress, sidestepped the pointed questions and in the end received a prolonged ovation. He waved away the accusations of corruption and said that the decision to dispatch troops to Tbilisi had been made by the entire Politburo.

Foreign Minister Eduard Shevardnadze, whose handling of foreign affairs has provoked criticism from conservatives, also received a barrage of pointed written questions.

Half of them concerned the Soviet Union's role in Eastern Europe and the controversy about a united Germany's role in NATO, he said. But Shevardnadze so ably defended Soviet foreign policy in preliminary remarks that he preempted the oral questioning that the other four Politburo members were subjected to and rushed to his seat amid a thunder of applause.

Questions to Prime Minister Nikolai Ryzhkov, a leading Politburo member, centered on his role in the Soviet economic program, which has drawn heavy fire.

Yakovlev, too, was called for questioning but escaped harsh attacks. He denied he had contributed to a worldwide collapse of socialism, saying, "If a people turns its back on the party, it is a matter for the people."