KANDAHAR, Afghanistan (AP) Heavy bombers went into action over northern Afghanistan on Wednesday, pounding front-line Taliban positions in a dramatic increase in U.S. support for opposition forces on the battlefield. In this southern stronghold, Taliban authorities took the first foreign journalists allowed into the city since the airstrikes began to the ruins of a hospital they claimed was badly damaged in U.S. military assaults earlier in the day. There was no independent confirmation of the claim, which said 15 people died and 25 were seriously wounded. Low-flying American jets and what appeared to be high-flying bombers struck Taliban positions about 30 miles north of Kabul, raising huge clouds of smoke as they unleashed bombs and missiles.