An express train travelling about 120 kilometres per hour has smashed into a truck at a crossing south of Tokyo in Japan, sparking a blaze and killing the truck's driver and injuring about 30 others.

Key points: It's believed the train was travelling at 120kph

It's believed the train was travelling at 120kph The train driver applied emergency breaks but was too late to prevent collision

The train driver applied emergency breaks but was too late to prevent collision Japanese trains have a well-deserved reputation for safety and punctuality

The crash derailed the train's front carriage and pinned the truck to a wall as it burst into flames, spewing black smoke into the air and its cargo of citrus fruit onto the tracks.

The force of the impact shattered the train's front window and bent an overhead power line.

Witnesses described an intense fire and panic among the 500 passengers on board as they sped through the crossing near Yokohama Station, south of Tokyo.

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

Local police confirmed it was the truck driver who died at the hospital about an hour after the accident.

The truck was believed to have entered a railway crossing in Yokohama. ( AP: Kenzaburo Fukuhara/Kyodo News )

Japan's national broadcaster NHK said the truck driver, 67, was pinned under the train. Another woman in her 20s was also seriously injured.

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

The company said it had launched an investigation into the accident that took place just before noon on Thursday (local time).

"The maximum speed there is set at 120 kph and we believe the train was travelling as fast as that," a Keikyu spokesman 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," the Keikyu spokesman said.

'It was a panic'

30 people were injured, and the driver of the truck died following the accident. ( AP: Eugene Hoshiko )

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 piled on top of each other.

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"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.

Earlier this year, 14 people suffered light injuries when a driverless train in suburban Tokyo went the wrong way and smashed into the buffers.

In April 2005, a speeding commuter train near Osaka jumped the tracks on a tight bend during the morning rush hour and smashed into an apartment tower. The driver and 106 passengers were killed and more than 550 people were injured.

The crash was Japan's worst rail disaster since 1963 when 161 people died in Yokohama after a freight train collided with a truck and was then hit by two passenger trains.

AFP