SEOUL, JULY 13 -- About 200 relatives of prisoners along with other activists occupied the top floor of South Korea's opposition party headquarters today, demanding a tougher stance in the party's negotiations with the government.

The confrontation was an early sign of tensions within the opposition, a coalition of many groups brought together by their common fight against the government, and it showed how difficult it may be for the opposition to compromise in those negotiations without alienating supporters.

Meanwhile, President Chun Doo Hwan, who has promised to step down next February, appointed a new prime minister for the second time in two months and replaced seven other Cabinet ministers.

The shuffle was billed as an effort to give the government a less partisan cast prior to a fall election, since several ruling party members were ousted. But Chun also appeared to strengthen his own hand with the appointment of five former military men.

Chun's new prime minister is Kim Chung Yul, a former Air Force general and ambassador to the United States. He replaces Lee Han Key, who was appointed May 26.

The new defense minister, Chung Ho Yong, is a military classmate of Chun, who took over in a military coup in 1980 and was elected the next year under a constitution drafted under martial law.

Opposition leaders expressed dissatisfaction with the reshuffle, saying Chun should appoint a truly civilian and neutral Cabinet to manage the government between now and the election.

Chun, who would be the first president to leave office voluntarily since independence in 1948, has promised to permit free presidential elections this fall. His promise, along with pledges of other major changes, followed 20 days of street demonstrations in June that revealed strong middle-class support for strengthened democracy.

Chun's choice to replace him is Roh Tae Woo, another former military colleague who now heads the ruling Democratic Justice Party. Roh is expected to shake up the party hierarchy Tuesday.

Both the ruling party and the opposition Reunification Democratic Party are finishing drafts of a new constitution that will mandate direct elections and incorporate other changes. Party officials expect to begin negotiating to resolve differences in the drafts later this week or next week.

The sit-in at opposition party headquarters began this morning when activists noisily stormed the building as opposition leader Kim Young Sam held a news conference. Demonstrators and party workers, who have been allies in years of antigovernment protests, yelled at and shoved each other, but no serious violence ensued.

The activists, many of whom had just been released from prison under Chun's partial amnesty for political prisoners, soon took over the fifth floor. The party moved into the building only last week, and late today colorful banners left over from the inauguration party still hung outside the building, next to new political banners demanding freedom for "patriotic fighters."

The government released 357 political prisoners last week and today released National Assemblyman Yoo Sung Hwan, who was jailed last year for saying that unification with North Korea should replace anticommunism as the nation's top goal.

But the opposition says many more political prisoners remain in jail. Diplomats here agree that a number of people, whose only crime was to express their opposition to the government, are still locked up.

The protesters demanded in a pamphlet that charges of all "evil actions," including torture and cover-up of torture cases, be investigated and all wrongdoers be punished. Kim Young Sam and Kim Dae Jung -- the other key opposition leader -- one or both of whom are likely to run for president against Roh, have said they would seek to avoid retribution if elected.

Both Kims visited the fifth floor this afternoon to listen to the activists' demands for about 45 minutes.

{The demonstrators filed out of the headquarters shortly after noon Tuesday, ending the sit-in peacefully after party leaders and demonstrators agreed to issue a joint statement calling for the release of all "prisoners of conscience." The statement also called for an investigation of the treatment of long-term prisoners and for dismantling of the internal security agencies, leaders of the sit-in said.}