Hundreds of radical students shouting "Oppose divisive Olympics!" battled riot police with firebombs and rocks Friday in an anti-government and anti-Olympic demonstration.

Clashes broke out at Yonsei University in western Seoul when riot police stopped about 600 students from marching off campus to protest Thursday's arrest of a student leader.Police arrested the head of the students' association on charges of having led an anti-Olympic campaign.

Students armed with scores of firebombs, rocks and clubs attacked riot police who responded with dozens of tear gas grenades and returned rocks.

Thousands of students remained indifferent inside the sprawling campus as clashes continued for half an hour along the fences, blocked off by about 1,000 riot police with plastic shields.

At least five students were seen bleeding in their faces when they were hit by stones. No arrests were reported.

"Oppose dictatorial Olympics suppressing democratic forces!" the students shouted, accusing the government of using the Olympics to perpetuate dictatorship and division of the Korean Peninsula.

The students retreated to the campus after vowing to continue their struggle until the release of the arrested student leader. But students said they want to stage a peaceful campaign.

Student leaders claimed the Olympics to be held Sept. 17-Oct. 2 in Seoul heightened the risk of war with communist North Korea, which has decided to boycott the Games after its demand to be a co-host was rejected.

The radicals, a small but powerful minority on campuses, lack public support.

Also Friday, police ordered a crackdown on leaflets denouncing the Olympics. Radical students have distributed leaflets in which they demanded the Olympics be shared with North Korea to ease tension and advance national unification.

Police said security guards arrested a student volunteer at the main Olympic stadium Thursday when the student was caught trying to bring in about 100 anti-Olympic leaflets.

In the southern city of Kwangju, police questioned 17 students arrested Thursday night when groups of students staged sporadic anti-government, anti-Olympic protests in downtown streets.