Police say a roadside bomb has struck a bus in northern Pakistan, killing three people including two security officials. Another passenger was injured in the attack on Monday in Kohistan district in Khyber Pakhtunkhwa province. The bus was heading to Dasu district, where the country’s biggest hydropower project is being built with Chinese help. No group has immediately claimed responsibility, but the Pakistani Taliban and other insurgents have a presence in the region. The Pakistani Taliban have stepped up attacks across the country in recent years.