text: Seoul embassies warned of terrorist attacks . SEOUL 1996-08-27 South Korea has told its overseas missions to step up security since its embassy in the former Yugoslavia received a threat over Seoul 's crackdown on radical students , the foreign ministry said on Tuesday . A letter to the Belgrade embassy on Monday under the name of the Macedonian Communist Party demanded South Korea release detained student leaders , a ministry spokesman said . " The letter said the party would assault the embassy , other South Korean-related facilities and Korean nationals unless our authorities released arrested students , " he said . Nearly 400 members of an outlawed student group were arrested after violent protests demanding reunification with communist North Korea were crushed by riot police at a Seoul university this month . Authorities branded the violence , in which a police officer was killed , as an act of terror . " The ministry has ordered the embassy to take urgent security measures against possible terrorist attacks , " the official said , asking not to be named . It had called for similar precautions at other overseas missions , including those in Canada and Bangladesh where leftist groups have staged protests over the crackdown .