PARACHINAR, Pakistan: A bomb ripped apart a minibus in a militant-infested area of northwestern Pakistan Monday, killing all 17 people on board and two others in a nearby vehicle, police said. The bus was traveling between the cities of Hangu and Kohat close to Pakistan's lawless tribal region. Islamist militants frequently carry out attacks in the area against both civilians and security forces. Hangu police chief Abdur Rasheed said the bomb that destroyed the bus contained high explosives, and the blast was especially deadly because the bomb detonated the gas cylinder used to power the bus. Authorities initially thought the gas cylinder alone caused the explosion. The explosion blew out the windows of a second minibus nearby and knocked it on its side, killing two people and wounding 10 others, two of them critically, said Rasheed. Local TV footage showed the twisted carcass of the first bus laying beside the road with little left except its wheels and undercarriage. The second bus rested on its side with blood spattered across its roof. More than 20 percent of the bombings and other attacks in Pakistan last year occurred in Khyber Pakhtunkhwa province where Hangu and Kohat are located, according to a recent report by the Pak Institute for Peace Studies. Roughly 35 percent took place in the tribal region. Overall, attacks in Pakistan declined nearly 20 percent last year as a result of Pakistani military operations, better surveillance by law enforcement agencies and the death of key militants in US drone strikes, the Islamabad-based think tank said.