Media playback is unsupported on your device Media caption The crash happened during the morning rush hour

At least six people have been killed in a collision between a passenger train and a bus in Canada's capital, Ottawa.

The front of the bus was ripped off in the crash, and some 30 people are in hospital, eight with critical injuries.

The crash between the double-decker and a Via Rail train occurred at the height of the morning rush hour.

Rebecca Guilbeault, who was on the bus with her young son, said people on board were screaming for the bus to stop.

"As I looked up the bus was coming into contact with the gate and the front of the bus, it like all impacted at once and everyone flew," Ms Guilbeault told the Associated Press.

"I've seen a few people dead, someone ripped in half," she said about the aftermath of the crash. "I just feel so bad. Honestly I am just a little shaken up right now."

The crash happened at about 08:48 (12:48 GMT) in the west end of the city, a more rural area surrounded by corn fields, and brought Via Rail's Ottawa-Toronto route to a halt.

'Boom!'

Ottawa University student Rob Gencarelli, who was on board the train, told CTV: "All I felt was a bump and then I saw smoke, and then we were going off the tracks. I thought we were going to flip over."

Image caption Transport officials are investigating at the scene

Eyewitnesses also reported seeing the bus driver going into a lowered barrier.

"Boom! It went into the train like that. He just didn't stop,'' Pascal Lolgis was quoted by the Associated Press as saying.

Another witness, Mark Cogan, told AP that the bus just kept going.

"The train is going through. And I was just looking around, just watching things happen. And noticed that in the bus lane, the double-decker bus," he said.

"I saw him, and he just kept going. He went through the guard rail and just hammered the train, and then it was just mayhem."

Among the dead is the driver of the bus, transit union president Craig Watson confirmed. Mr Watson did not identify the driver but said he was in his early 40s and had been with the bus company for about 10 years.

Eight people injured in the crash were listed in critical condition as of Wednesday evening.

The lead investigator for Canada's National Transportation Safety Board (TSB), Glen Pilon, said Via Rail crossings at streets have been a concern because they are carrying passengers instead of cargo.

The county has seen 257 accidents involving passenger trains colliding with vehicles at level crossings over the last decade, the safety board said on Wednesday.

Mr Pilon said a priority for investigators was getting the train's black box recording to determine what happened in the moments before the crash.

"That will give us the speed and what was going on," he said.

The TSB said it was a very complex investigation that could take several months. A team is already assessing the crossing's design and sightlines, and checking the warning systems.

Canadian Prime Minister Stephen Harper posted a message on Twitter saying he was "deeply saddened" and that his "thoughts and prayers are with the families of those involved".

It is Canada's worst rail accident since a train carrying crude oil derailed and exploded in a Quebec town in July, killing 47 people.