Riot police arrested a band of radical students Thursday after they stormed into the office of a governing party lawmaker with iron pipes and firebombs and shouted anti-U.S. and anti-government slogans.

Students broke windows and unfolded a giant placard that read "Drive out Yankees" and "Arrest (former president) Chun Doo-hwan." Students threatened to burn the office or jump from windows if police intervened.Police were backed up by fire trucks and hundreds more police who spread sponge mattresses around the building to prevent suicide attempts.