Police are hunting for two males who allegedly assaulted a 13-year-old boy and left another seriously injured at the scene of a crash as they stole two e-bikes in Melbourne’s east.

Investigators have been told two 13-year-old boys were riding their e-bikes along Koonung Creek Trail in Doncaster East around 5pm on Monday when two masked males approached them.

The offenders first assaulted one of the boys and stole his e-bike, police said.

Police have released an image of the stolen bikes in the hope anyone who was in the area at the time recognises them and can come forward with information.Police have released an image of the stolen bikes in the hope anyone who was in the area at the time recognises them and can come forward with information. (Nine)

The boy was able to run from the scene with minor injuries, which did not require medical treatment.

The second victim fled on his bike in fear and was chased by the offenders, police said.

He crashed into a wall near the Blackburn Road underpass and suffered serious injuries.

The offenders then caught up with the injured boy, stole his bike and rode off without assisting him.

The 13-year-old was taken to hospital with critical injuries including skull fractures, a severely broken leg and broken nose.The 13-year-old was taken to hospital with critical injuries including skull fractures, a severely broken leg and broken nose. (Twitter)

The 13-year-old was taken to hospital with critical injuries including skull fractures, a severely broken leg and a broken nose.

“He’s still in quite a serious condition, so much so that we haven’t been able to speak to him personally to see what he remembers,” Senior Constable Liam Webb said.

“It’s quite deplorable seeing another human being laying down, in the bush, in pain, to just take his bike and ride off without rendering any help, it’s quite disgusting.”

Both offenders are described as Caucasian, around 15 years old, 165cm tall, and were wearing black ski masks and black clothing.

One offender had black hair and was wearing a multi-coloured BAPE hoodie.

Police have released an image of the stolen bikes in the hope anyone who was in the area at the time recognises them and can come forward with information.