SEOUL, NOV. 12 -- Facing a sudden barrage of criticism from opponents, ruling party presidential candidate Roh Tae Woo made his first detailed defense today of the controversial 1979 coup that brought President Chun Doo Hwan to power.

Roh said the military takeover had been necessary to avert political chaos in South Korea.

A former general, Roh has been put on the defensive by a series of charges from the opposition this week over his disputed role during the coup. The accusations are forcing Roh and the ruling Democratic Justice Party to break a virtual eight-year silence on the previously taboo issue.

The public debate could set back Roh's hopes for shedding an image as a close Chun ally and key actor in the military's seizure of power.

In an interview with senior Korean journalists, Roh, one of four major candidates in the December election, said the assassination of President Park Chung Hee in October 1979 created a power vacuum.

"The military was the last resort to contain social and political chaos," Roh said. "It would have been very dangerous if the military had faltered . . . . The troops were mobilized to save the nation."

But Roh denied that the takeover, which he and Chun led two months later after Park's assassination, amounted to a coup. In the takeover, troops of Chun and Roh arrested Army Chief of Staff Chung Sung Hwa, who had declared military rule. Chun and Roh's takeover was the key move, according to most western diplomats and political analysts, that paved the way for Chun to take full control in South Korea.

"We did not intend to take power," he claimed. "It is not proper at all to link the incident with a coup." When a reporter noted that the generals involved in the takeover received posts in government and business, Roh insisted that "I did not desire to become a politician or a presidential candidate," Roh said. "I think it is my fate, shaped by the conditions of an era."

Nationwide demonstrations last June opened a new political atmosphere that eased a taboo on public debate of the 1979 takeover. Until now, however, Roh has managed to sidestep opposition charges that the move was an illegitimate grab for power by the generals.

Roh was forced to respond after Chung, the Army chief he helped topple, emerged from years of obscurity to endorse opposition candidate Kim Young Sam. Chung, who was convicted in a widely discredited trial of having helped assassinate Park, vowed to tell his side of the story.

Since Chung's announcement, people have been snapping up early editions of newspapers to read about his charges and the ruling party's responses. Outside the Korea Press Center in downtown Seoul, Koreans have clustered around copies of newspapers posted in public display cases to read accounts of the takeover, which has been shrouded in official mystery.

Chung, the former Army chief, who was demoted to private and jailed under Chun, surprised the ruling Democratic Justice Party by endorsing Kim. The party was initially silent. Then a top party official tried briefly to deny Roh's role in the coup.

Yoo Hak Seong, a senior party official who was an assistant defense minister at the time of the coup, held a hastily arranged press conference Wednesday to announce that he, and not Roh, had given the order for Roh's troops to move from frontline posts to Seoul to help arrest Chung. Most observers found this hard to believe, as Yoo's rank did not give him authority to move the troops.

In his comments tonight, Roh contradicted a key part of Yoo's version of events. Roh claimed personal responsibility for withdrawing the troops from their strategically important border positions. But, he insisted, precautions had been taken to avoid weakening the country's front with North Korea.

Kim Young Sam has accused Roh of endangering national security by taking soldiers out of the border area, where most of the South Korean Army is normally deployed.