More than a dozen rockets slammed into Afghanistan's capital of Kabul today, killing 14 people and injuring 10, Afghan state radio reported. No one immediately claimed repsonsibility for the attack. But the Radio Kabul broadcast, monitored in Islamabad, blamed ``extremists,'' presumably referring to U.S.-backed guerrillas headquartered in Pakistan. Moslem insurgents have been fighting for more than a decade to topple Afghanistan's Communist-style government. In the past year, hundreds of people have died and thousands more injured in rocket assaults on the Afghan capital.