A large gathering of South Korean students denounced the country's military-backed government today, demanding an immediate end to martial law and the removal of officials left in power after the death of president Park Chung Hee.

Several thousand students from 13 colleges around the country specifically called for the dismissal of a key military leader Gen. Chun Doo Hwan, who recently became head of the Korean Central Intelligence Agency.

Neither police nor military forces interfered with the large, illegal rally at National University in Seoul, indicating that authorities hope the student unrest will run its course without provoking massive confrontations.

There were also signs the students wanted to avoid that, too. They did not leave the campus grounds to face riot police stationed outside. And a National University student group indicated it would drop a boycott of military drills, a boycott that had put them on a collision course with military officials.

Nevertheless, the latest protests, coupled with an unprecedented wave of labor strikes, have raised fears of a major confrontation with martial law authorities and a new cycle of violent suppression.

Both the labor strikes and student protests are illegal under the martial law rules imposed when president Park was assassinated last October. The martial law command has condemmed the unrest but so far has not intervened, honoring a series of compromises worked out by civilian leaders hoping to move South Korea away from the severe repression of Park's reign.

Civilian officials moved to free campuses from government surveillance, gave fired professors their jobs back, and agreed to permit demonstrations on campus.

A wave of campus protests, most of them involving college issues and military training, began several weeks ago but were carried out peacefully as police abided by the agreement not to make arrests on campuses.

However, last night more than a thousand students at Sungkyunkwan University here marched off campus, clashing with riot police, and a similar incident occurred 150 miles to the south in Taejon.

The immediate issue at Sungkyunkwan was the threatened drafting of more than 80 students who has refused to take part in a 10-day military training on an Army base, a requirement of all male college freshmen. The hundreds of marchers were supporting their refusal to drill and denouncing their threatened conscription.

On Sungkyunkwan's hilly campus in eastern Seoul this afternoon it was apparent there were many who doubted the wisdom of confronting authorities on the military drill issue.

A meeting of those threatened with the draft for refusing drill sessions was split almost evenly between those who wanted to press their protest to the finish and those who drew back. The latter group argued that a continued refusal would give the martial law command an excuse to clamp down tightly on students, using the issue of national secutiry as an excuse.

Until recently, students has largely confined their protests to college issues.

But the large gathering at Seoul National University this afternoon showed a concentration on broader issues, including the immediate abolition of martial law. Gen. Chun, who has risen rapidly in power since Park's death, said earlier this week conditions are not ready for ending martial law.