Radical students fought riot police with firebombs and rocks in a demonstration Friday demanding an end to U.S. pressure to open Korean trade and agriculture markets.

As anger over trade issues increased, the nation's major dissident and radical student organizations announced nationwide protests to be held Sunday. Police said illegal protests would be blocked and security would be tightened around U.S. facilities."I admit we have not made enough effort to remove misunderstanding," Deputy Premier Lee Seung-yun told reporters Friday.

Lee, also the economic planning minister, said the government would try to resolve trade disputes with foreign governments, especially Washington.