Missing Melbourne teenager found after widespread search

A teenager has been found 45km from where he went missing three days ago on Victoria's Mornington Peninsula, sparking major concern from police and his family.

The 14-year-old, who lives with autism, was found under a bridge in Mordialloc in Melbourne's south-east this afternoon, hours after his parents spoke to media to plead for help to find him.

He who reportedly had not had food or water for days, has been taken to the police station to meet with his parents, before he'll be transported to hospital for observation.

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He was last seen leaving a property on Glencoe Crescent in Mount Martha about 11.20am on Friday.

"We are concerned. He left home with a backpack and didn't take his phone," his mother told media this morning.

"He has been up and down over the past couple of weeks."