At least six people, including a tribal leader, were killed in a bomb blast in Pakistan's northwestern tribal region on Monday, a media report said.Duniya news said the tribal leader, Muhammad Jaan, was going to a neighbouring village when a remote-controlled blast blew up his vehicle in Kamarsar area of district Mamoond in Bajaur Agency, a tribal area bordering Afghanistan.Those killed included the leader besides his five friends who were in the vehicle which was destroyed in the explosion. Several passersby were also injured.Police said the bomb was triggered by a remote-controlled device as soon as the vehicle passed by it.