AMMAN, Sept 23 (Reuters) - The Jordanian army said on Tuesday it had mounted air strikes against 'terrorist groups' that were planning attacks in Jordan, an indication Amman had joined U.S.-led air strikes against Islamic State in neighboring Syria. A Jordanian army statement did not say where the air force had struck. 'Air force jets destroyed a number of targets that belong to some terrorist groups that sought to commit terror acts inside Jordan,' the statement broadcast on state TV said.