QALAI DASHT, Afghanistan -- U.S. warplanes bombarded Taliban positions Sunday near a front line north of the capital, Kabul, marking what could be the start of a more aggressive campaign on behalf of opposition forces fighting the Islamic regime. \nIn Kabul, meanwhile, grieving neighbors pulled dust-covered bodies of seven civilians -- three women and four children -- from the ruins of two homes destroyed Sunday by a U.S. bomb. "This pilot was like he was blind!" sobbed one neighbor. \nAlso Sunday, the British Broadcasting Corp. quoted an Afghan doctor as saying the 10-year-old son of Taliban leader Mullah Mohammed Omar was killed during U.S.-led strikes. The boy died on the first night of bombing raids on the Taliban stronghold of Kandahar, said Dr. Abdul Barri. \nBarri, who spoke to the BBC as he crossed the border into Pakistan, said that Omar's uncle was hit in the same raid but was believed to still be alive and receiving treatment at the hospital at Kandahar. \nIn Pakistan, the U.N. refugee agency renewed appeals Sunday for Afghanistan's neighbors to open their borders to the refugees -- including up to 15,000 trapped on the "no man's land"near the Pakistani town of Chaman. \nThe attacks Sunday marked the closest and most intense U.S. strikes so far against Taliban positions defending Kabul from northern alliance forces, which have been stalled for years 12 to 25 miles north of the city. \nU.S. jets streaked over the opposition-held Panjshir Valley, and opposition officials told an Associated Press reporter in the area that they appeared to strike Taliban positions about one mile behind the front line. \nSeveral eyewitnesses, including journalists and residents, also reported Taliban positions bombed in the area. \n"We are hoping this will be a big help for the future of our forces," Waisuddin Salik, an opposition spokesman, said.