SEOUL, April 1 : South Korea said on Wednesday it would further tighten driving restrictions for public sector workers, as Asia's fourth-largest economy raised its resource security crisis alert in the face of the Middle East crisis. South Korea is raising its energy security alert to a "warning" as of Thursday, the energy ministry said, up from "caution" and "concern" levels issued during March due to prolonged instability in the Middle East heightening uncertainty over energy supply. The