A car bomb devastated a busy street in northwest Pakistan on Friday, killing at least 20 people, injuring scores more and unnerving a region already dangerously on edge after the attacks on India's commercial capital last week. Escalating violence is destabilizing Pakistan's northwest just as the country faces accusations from archrival India that the gunmen behind the carnage in Mumbai were trained in Pakistan and steered by militants based there. Neither the motive nor the culprits behind the Friday evening blast in Peshawar were clear. But provincial government chief Haider Khan Hoti said "external forces" could be to blame - a comment understood in Pakistan to mean India. The bomb went off near Peshawar's famed Storytellers Bazaar early Friday evening, wrecking a Shiite Muslim mosque and a hotel and setting a string of vehicles and shops ablaze.