ISLAMABAD (Reuters) - A huge explosion rocked Pakistan's main northwestern city of Peshawar on Saturday, police and residents said. "It was a very big explosion. I could see smoke rising from the scene," Asad Ali, a resident, said by telephone from Peshawar. Police said they were investigating. A Taliban suicide bomber earlier crashed his explosives-laden truck into a police station in Bannu, also in northwestern Pakistan, killing six people and wounding 30, police said.