At least ten people were killed and dozens more injured in an explosion in northern Pakistan. The suspected car bomb went off in the city of Peshawar. The blast hit a passing school bus killing at least four children. No-one has yet admitted the attack, which comes as the Pakistan army continues to fight the Taliban in the Swat Valley.Peshawar is the capital of the North West Frontier Province, where the army has been ordered to crush the militants. Hundreds of thousands of people have fled the fighting, and the United Nations has warned of a looming humanitarian tragedy. Rising violence has also sparked fears for the stability of Pakistan, which is equipped with nuclear weapons.