KARACHI - A blast hit a bus carrying Pakistani navy officials in Karachi on Thursday, wounding 15 people, a provincial government official said, the third attack on the navy in less than a week."Till now we have reports that 15 people have been injured," said Sharfuddin Memom, a spokesman for the Sindh provincial government. Karachi is capital of Sindh.Two bombs hit buses carrying navy personnel on Tuesday, killing four people and wounding 56.