Police have interviewed a 48-year-old man with "no apparent motive" who allegedly killed a bus driver by setting him alight at a stop in suburban Brisbane, leaving morning commuters and onlookers horrified.

Key points: Police say there is "no apparent motive" but a link to terrorism had been ruled out

Police say there is "no apparent motive" but a link to terrorism had been ruled out Man, 48, in custody and cooperating with police

Man, 48, in custody and cooperating with police Six people on the burning bus at the time helped out by onlookers

Six people were on the council bus at the time of the attack on 29-year-old Manmeet Alisher, who was also known as Manmeet Sharma, with a number treated for minor injuries and smoke inhalation, police said.

Queensland Police Superintendent Jim Keogh said a 48-year-old man had been taken into police custody after he allegedly threw a device and while there was "no apparent motive" he had ruled out a link to terrorism.

"Words escape me, it's a horrific incident here in the quiet suburb of Moorooka," Superintendent Keogh said.

"A bus driver, going about doing his business, supporting the community, has had his life taken from him in what is a senseless and needless act.

Bus driver Manmeet Alisher was killed in the attack. ( Facebook: Manmeet Alisher )

"The fire was substantial, he would have stood little chance."

Onlookers broke through the back doors of the bus to get the passengers out.

Superintendent Keogh said the passengers were visibly shaken and considered themselves lucky.

"It's lucky the whole bus didn't become engulfed in flames.

"They are traumatised ... it was rather rapid."

Queensland Police Commissioner Ian Stewart said it appeared as passengers boarded the bus "a man threw some type of incendiary device at the driver".

A man, 48, is in police custody after the alleged attack. ( ABC News: Casey Briggs )

Passengers 'lucky to survive'

Sorry, this video has expired 'A senseless, needless taking of a young life': Queensland police

Taxi driver Aguek Nyok was walking past the bus when the fire started and said he kicked in the bus's back door to free trapped passengers.

"Unfortunately I couldn't go inside because there were fumes," he said.

"It was smoky, you can't even think of going there, and the fire was getting higher and higher."

Superintendent Keogh praised the response.

"He certainly jeopardised his own life for the safety of those on the bus," he said.

A witness said there were children on the bus at the time of the attack. ( ABC News: James Maasdorp )

One witness said she helped passengers, including some young children, get off the bus.

"They were lucky to survive," she said.

"[They were] just small children, [their] mum was screaming.

"I was scared."

Aster Benebru, the owner of a nearby bakery, said her shop on Beaudesert Road was closed at the time of the fire, but she gave a man an extinguisher to help battle the blaze.

"When I go I saw the bus burn, smoke coming [out]," she said.

Passengers on the bus at the time of the attack were freed by passers-by. ( ABC News: James Maasdorp )

Brisbane Mayor Graham Quirk asked public transport users to show appreciation to drivers today, more than ever.

"It is a very, very sad day for council and the wider community — to see the loss of one of our drivers and in this way," he said.

He said the council would offer counselling to all of its bus drivers, and the council would pay tribute to Mr Alisher.

"One thing we will be doing as an organisation tomorrow is to fly the flags of Brisbane at half mast as a mark of respect to our bus operator - it's just a very, very sad set of circumstances," he said.

He said an on board camera captured the attack.

"Footage has been provided to the Queensland Police Service to assist them with their investigations at this time," he said.

"The advice that I am getting from police is that this is a random act."

Deputy Mayor Adrian Schrinner said council's thoughts and prayers were with the driver's relatives and friends.

Mr Alisher was also a well-known singer and entertainer in Brisbane's Indian community.

"We lost a member of the Council family — the Brisbane family — today with the senseless and inexplicable murder of one of our bus drivers," Councillor Schrinner said.

"The best thing we can do as a community at this time is to show all of our bus drivers the appreciation and respect we have for them."

Rail, Tram and Bus Union (RTBU) spokesman Tom Brown said the man's colleagues were in shock.

"We've organised grief counsellors and they're at the depots now and I'm heading there ... as well to see if I can assist and there will be further counselling as well made available," he said.

Passenger 'absolutely beside herself'

Police said there was no clear motive for the attack. ( ABC News: James Maasdorp )

Andrea Savage and her baby daughter were planning to catch the bus but were running late.

However, an acquaintance of hers was on the bus, with two children.

"Her youngest nearly got trampled by people trying to get off in the smoke-filled cabin, she was clutching at her little ones," she said.

"When I saw her she was just absolutely beside herself.

"This is the first time I've been thankful for running late."

State Transport Minister Stirling Hinchliffe told 612 ABC Brisbane the incident would be considered in a review of bus driver safety already underway.

"This has been an issue that has been of concern [although] not with incidents such as the nature of this extraordinary and terrible one today," Mr Hinchliffe said.

"The nature of this incident will clearly be a matter that will be of great interest to that review process.

"That review process was designed to involve the Queensland Police Service, so the experiences that they've had, and Brisbane Transport, will be very important to that review."