RAS LANOUF, Libya — Libyan warplanes launched multiple airstrikes Monday on opposition fighters regrouping at an oil port on the Mediterranean coast, the second day of a harsh government counteroffensive to thwart a rebel advance toward Moammar Gadhafi's stronghold in the capital Tripoli.(SCROLL DOWN FOR LATEST UPDATES)The counteroffensive has halted a rebel attempt that began last week to extend their control beyond the eastern half of the country, in opposition hands since after the revolt to oust Gadhafi began on Feb.