South Korea has increased vigilance against additional provocations by North Korea in the wake of its rocket launches seen as a show of protest against ongoing joint military drills between Seoul and Washington, the defense ministry here said Monday. In the latest in a recent series of launches, Pyongyang fired 25 short-range rockets into waters off its east coast Sunday evening, which flew about 70 kilometers. The South Korean military judged the rockets to be FROG short-range surface-to-surface missiles, which the North introduced in the 1960s