A train is seen as it is derailed after a collision with a truck in Yokohama, near Tokyo, Japan on Thursday. Reuters

One person was killed and around 30 people injured on Thursday, authorities said, when an express train and a truck collided on a busy line connecting Tokyo and Yokohama.

The accident derailed the front carriage of the train and badly damaged the truck, which burst into flames and spewed its cargo of hundreds of oranges and lemons alongside the tracks.

Police are seen on site after a train derailed during a collision with a truck in Yokohama, near Tokyo, Japan.

The train's front window was completely smashed and the truck appeared to be pinned to a wall just beyond the crossing where the collision took place.

"Emergency crews took 30 injured people into care. Of those, two had sustained serious injuries. Of those severely injured, the hospital has confirmed the death of one person," a fire department official told reporters at the scene.

According to the Keikyu train company operating the service, the driver said he had applied the emergency brake but too late to prevent the collision.

The company said it had launched an investigation into the accident that took place just before noon as the express train, carrying 500 people, hurtled through the crossing.

"The maximum speed there is set at 120km (75 miles) per hour and we believe the train was travelling as fast as that," a Keikyu spokesman, who declined to be named, told AFP.

"There is an abnormality detection system there for emergencies and cases such as a truck getting stuck on the crossing. This system kicked in and an alarm signal was flickering," added this spokesman.

'It was a panic'

Eyewitnesses spoke of a fierce fire and panic, with TV images showing terrified passengers streaming from the carriages after the collision.

One man who was travelling in the first carriage told national broadcaster NHK there was a "sudden sound" and that the impact left people in heaps.

"I saw flames. Then the fire became more and more intense. So everyone rushed to get outside. It was a panic," this eyewitness said.

Another person who witnessed the scene said there were flames coming from the bottom of the truck and that the "smoke was awful."

Japanese trains have a well-deserved reputation for safety and punctuality and accidents are rare.