Two people were killed when a Sydney to Melbourne express train derailed near the Victorian town of Wallan, officials say.

Several other passengers were being treated for injuries, emergency services said.

One person was airlifted to a hospital in Melbourne.

Images showed a number of twisted carriages had left the track, with one on its side. It was unclear what caused the train to derail.

The train was reportedly carrying 160 passengers and five crew members when it left the tracks at about 19:50 local time (08:50 GMT) on Thursday, some 45km (28 miles) north of Melbourne, the Victorian state capital.

It is understood to be the main long-distance service between Melbourne and Sydney.