Nikkei up on bargain hunting but China worries cap rise

TOKYO, July 7 (Reuters) - Japan's Nikkei share average rebounded on Tuesday as bargain hunters stepped in a day after Greek angst triggered a sharp fall, but uncertainty over China's efforts to rescue its slumping stock market capped further gains. The Nikkei share average gained 1.3 percent to 20,376.59, after tumbling 2.1 percent the previous day in a knee-jerk reaction to rejection of austerity measures by Greek voters. The broader Topix rose 1 percent to 1,637.23 and the JPX-Nikkei I