SEOUL, NOV. 17 -- South Korea's main opposition grouping today issued a list of charges against ruling party presidential candidate Roh Tae Woo for his part in a coup eight years ago, escalating the rhetoric and tension of what has quickly become a bitter campaign.

Opposition candidate Kim Young Sam's Reunification Democratic Party launched its attack in the form of 12 questions about the 1979 coup that it challenged Roh to answer. But the questionnaire was, in fact, a broadside that accused Roh of conspiracy, rebellion, jeopardizing national security and committing crimes, torture and other "inhumane atrocities."

The opposition party also called for a public accounting of those responsible for homicide on the night of the coup, the closest it has come to demanding punishment for past military misdeeds. Until now, opposition leaders have scrupulously maintained that they do not seek retaliation, which many fear could invite another Army coup.

South Korea's first free election in 16 years is scheduled for Dec. 16 as a result of widespread street demonstrations for democracy in June. President Chun Doo Hwan, who took power in the 1979 coup, has promised to step down in February, and Roh, his chosen successor, is battling three other major candidates to succeed him.

The attack today was all the more extraordinary since until recently, Chun's government permitted no public discussion of the events of 1979 and 1980 that put him in office.

Lee Min Sup, a spokesman for the ruling party, said there would be no response to the questionnaire, which he labeled a "replay of black propaganda and whistle-blowing tactics." Roh, who has tried to distance himself from Chun and from his own military background, last week was forced to defend the takeover, saying it was essential for the nation's stability after the assassination in October 1979 of president Park Chung Hee.

"At that time, the military was the last resort to contain the social and political chaos," Roh said.

But the opposition today rejected his explanation and presented new and detailed allegations about the affair.

Roh, Chun and a handful of other generals mobilized several thousand troops on the night of Dec. 12 and arrested Gen. Chung Sung Hwa, then Army chief of staff. Chung, who was then demoted to private and sentenced to jail for allegedly conspiring in Park's assassination, last week emerged from political hibernation to join Kim Young Sam's campaign.

The Dec. 12 incident paved the way for Chun to take power, which he did in stages through the following spring and summer. He eventually promulgated a new constitution that allowed him to be acclaimed president without real opposition.

Kim Young Sam's party said that Roh and others subjected Chung to water torture after his arrest. Roh also ordered troops away from the North Korean border, threatened then president Choi Kyu Hah to obtain retroactive approval for Chung's arrest and ignored repeated orders from the defense minister and other superior officers to desist, the opposition charged.

The coup makers also were responsible for killing and injuring several officers during shootouts on Dec. 12 and 13, the statement said.