A passenger threw an incendiary device at a Brisbane bus driver, setting him alight and killing him, Queensland's police commissioner says.
Ian Stewart says counter-terrorism authorities are involved in a homicide investigation sparked by Friday's fatal attack by a passenger on a bus at Moorooka, but he says there is nothing to suggest any terrorism-related links at this point.
He also says there's no indication the attack was racially motivated.
Mr Stewart said six passengers on the bus were taken to hospital suffering smoke inhalation and minor injuries.
He paid tribute to the heroic actions of a taxi driver who saw what was happening on the bus and kicked in the rear door of the burning bus, allowing them to escape.
A 48-year-old man is in custody over the attack that killed Manmeet Alisher, 29, on Friday morning.
"While we don't know the actual motives at this stage, I want to reassure the community that we take these incidents very seriously and that is why, as a precaution, officers from the State Security and Counter Terrorism Group have also been involved in this investigation," he told reporters.
"I want to assure you that there is no evidence at this time of any linkage to terrorist-type activities and certainly that has not become evident through the ongoing investigations that have occurred."
He added: "We do not believe at this stage that there is any evidence linking this to a racial complaint or concern by either of the people involved."
Mr Stewart appealed to anyone who might have footage of the attack to come forward.
He said witnesses had been traumatised by what they saw, and the attack was weighing heavily on the state just a few days after four people died on a ride at Dreamworld on the Gold Coast.
"We've rarely had a week where so much tragedy has occurred," he said.
© AAP 2016