South Korean police have arrested 5,739 people in Seoul in a massive law-and-order crackdown triggered by an unprecedented attack on a U.S. cultural center, authorities said yesterday.

The government announced a reward of nearly $28,000 for information leading to the apprehension of Jung Soon Chun, the suspected leader of a group of youths who set fire to the U.S. government's information office in the port city of Pusan Thursday. A Korean student died in the fire, and three others were injured.

Officials said 10,000 Seoul police officers were mobilized Friday night for the crackdown. Most of the arrests were for disorderly conduct, traffic violations and stealing, they said.

Of those rounded up, 3,877 were tried by police and fined or given short prison sentences, 1,663 were released with a warning and 199 released pending the completion of investigations, police said. Figures for the rest of the country were unavailable.

Police also stepped up patrols around foreign diplomatic residences. The attack on the U.S. information office in Pusan was the first on an American diplomatic facility in South Korea. Government authorities blamed dissident youths aiming "at causing social disorder and hurting U.S.-Korean relations."

Police said Jung, 27, a college dropout, has been in hiding since Dec. 9, 1980, when he led an abortive plot to set fire to a U.S. information office in Kwangju where an antigovernment uprising broke out that same year.