NEW : Pakistan says troops take village of Sharif . About 28,000 Pakistani troops move into epicenter of Taliban activity . Up to 10,000 militants are in North Waziristan , officials estimate . Hundreds of thousands of civilians fleeing Taliban , U.N. refugee agency says .
NEW : Official says troops take village of Kotkai . About 28,000 Pakistani soldiers move into epicenter of Taliban activity . Up to 10,000 militants operating in South Waziristan , officials estimate . Tens of thousands of civilians fleeing region , U.N. refugee agency says .