The role played by the South Korean military on the night of President Park Chung Hee's assassination has emerged as the biggest among many mysteries still surrounding the murder.

Sources with access to facts in the cntinuing investigation are inclined to doubt that there was military complicity in the murder.

But Seoul's busy rumor mill is fed with reports that some military leaders were approached shortly after the killing with a plea by the alleged assassin to seize the moment and take quick control of the government.

In one account derived from governmnet sources, Gen. Chung Sung Wha is reported to have been near the scene of the murder and to have met with the accused killer, Kim Jae Kyu, shortly afterward.

Gen. Chung is the Army's chief of staff who since the assassination has emerged as martial law commander and is regarded as the most powerful man in the group of civilian and military leaders now making day-to-day decisions.

An investigation supervised by his martial law command has reported that Kim, who was director of the Korean Central Intelligence Agency, killed Park in a KCIA dining room Friday night.

The official accounts published so far say only that Kim was later arrested by military authorities, but they give no explanation of his activities immediately after the slaying.

A more complete report was scheduled to be published two days ago but has been delayed for unexplained reasons. Martial law authorities, assisted by civilan prosecutors and national police, are conducting the investigation.

In the account widely accepted by well-informed South Koreans, these events took place immediately after the shooting:

Kim met with Gen. Chung in a house near the KCIA compound. They are known to have been good friends and originally were scheduled to dine together that night. Instead, Kim was instructed to have dinner with Park on that evening.

As Chung and Kim rode in an automobile toward a different KCIA headquarters building, Kim asked the general either to declare martial law immediately or to mobilize certain military forces to take control of the government.

Instead, Chung insisted that they go to a military headquarters, either to Army headquarters or to the Ministry of Defense. After they arrived, Kim was detained and ultimately arrested pending an investigation.

It is known that an emergency cabinet meeting was held at the Defense Ministry at 11 p.m., about 2 1/2 hours after the president had been shot. Out of it came the order placing almost the entire country under martial law.

One source said this week that it was merely coincidental that Chung was present on that evening and in touch with Kim. This source said that at first Kim did not acknowledge that he had been involved in the assassination and that it was not until another person present during the shootings began to talk that the military officials and cabinet ministers were aware of Kim's direct involvement. That person was said to be Kim Kae Won, chief secretary to the president and the only one in his entourage that night to survive the shootings.

This source, who has access to government information on the circumstances, said he had been informed that Gen. Chung had not been involved in the plot.

"There is no reason to think that he was a coconspirator," he said.

These sources also said there is still no clear explanation of Kim's motivation in killing the president. The government's public accounts say he was angry about past accusations, made against him by Park and his chief bodyguard, and that Kim feared dismissal as part of a major government shakeup.

Meanwhile, the military authorities today continued their drive to take control of the institution that the accused murderer once headed, the KCIA.

Reliable sources said that at least 80 KCIA officials and personnel have been held for questions to determine whether they had participated in the plot. Besides Kim, five of his personal associates in the agency have been interrogated.

Many other KCIA agents have been displaced by Army counterintelligence agents, leaving the once-powerful intelligence and counterespionage apparatus in disarray.

There were signs today that the military leaders intend to relax the martial law rules imposed at 4 a.m. on the morning after the shooting.

The martial law command announced that South Korea's normal four-hour curfew will be reinstated in eight rural provinces. A six-hour curfew, running from 10 p.m. to four a.m., had been imposed after the assassination. Seoul and other metropolitan areas will remain under the six-hour curfew.

Several cabinet members and military authorities continued their daily meetings and for the second day met at the residence of Choi Kyu Hah, the former prime minister who was automatically elevated to acting president after Park's death. There was no announcement concerning what was discussed.

It was announced that Secretary of State Cyrus Vance will head the U.S. delegation to Park's funeral on Saturday. He will be accompanied by Assistant Secretary Richard Holbrooke and several congressmen, the announcement said.

The government has not issued formal invitations for heads of state to attend the funeral but missions from about 15 countries have indicated they will come to Seoul. Prime Minister Masayoski Ohira of Japan is the only head of state expected to attend.