The US has flown a B-52 bomber over South Korea in a show of force after North Korea said it successfully tested a hydrogen bomb. <br /> <br />The B-52, which was flanked by US and South Korean fighter jets, swooped over an air base close to the North-South border. <br />North Korea said it detonated an underground device earlier this week to widespread condemnation, but experts remain sceptical about the claim.
