SOUTH KOREA put its 650,000 troops on increased alert Thursday, saying it feared North Korea could provoke border clashes to turn attention away from internal problems such as acute food shortages . . . EIGHT GUNMEN were killed in a shootout with police in the Colombian capital of Bogota on Thursday during a foiled attempt to hijack an armored Brinks truck carrying $600,000 in cash, police said . . . FEDERAL INVESTIGATORS combed a wheat field in Caddo Mills, Texas, for clues as to why two small airplanes collided, killing three people. Skies were clear Wednesday morning when the planes crashed, sending both four-seat aircraft plummeting to the ground . . . ISRAELI HELICOPTER gunships targeted guerrilla positions in southern Lebanon Thursday after a gunbattle in which three guerrillas and an Israeli soldier were reported killed.