Missing, feared dead: Mahmoud Hrouk. Photo: Facebook

A mother and father were searching for their teenage son, when they peered into the window of a house and saw the unimaginable on Sunday.

The Villawood parents of Mahmoud Hrouk, 16, spoke to their son about 9.30pm on Saturday.

When he failed to return home and could not be located or contacted, they reported to police that he was missing.

They were told by someone who knows their son that he could be at a house in Belmore Street, Fairfield East.

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When they arrived at the house on Sunday morning, they found a bloodied body on the floor, police said.

"They went to that address and found, from looking inside a window, what appeared to be a body inside the premises," Fairfield police acting Commander Steven Thomas said on Monday.

"The male has sustained serious, very brutal head injuries as a result of his death," he said.

Later, Mahmoud's silver and blue mountain bike was found about 200 metres from the house.

Acting Commander Thomas said the teenager was last seen at Villawood McDonald's about 6.30pm on Saturday.

He said police were desperate to speak to any of the boy's associates and to know whether anyone saw him riding his bike in the streets of Belmore, Bligh or Lupin streets at the weekend.

Police would also like to speak to anyone who knew of other people who might visit the house.  

Some neighbours have said they believe the single-storey house has been vacant for the past few months.

Acting Commander Thomas said Mahmoud's parents were "very distraught" and that he was not known to police.

"Information was given to us through family that he may have frequented that address," he said.

Forensic officers spent most of Sunday bagging evidence and were seen covering Mahmoud's bike with brown paper before taking it away for analysis.

Acting Commander Thomas said the teenager's body had yet to be formally identified but his parents had released a photo of him so that his last known movements could be tracked.

"How would any family be doing in circumstances where obviously a son is still missing and a young person has been found at a location where ... he may have gone to?" he said.

"So they are distraught by the whole situation and they are getting support from police and other family members."

Police said they had a number of leads and were looking at persons that could be associated with Mahmoud.

"We need the assistance of the public," police said.

Contrary to media reports, acting Commander Thomas said he had no information to suggest the house where the body was found was a known place for squatters.

"Police are obviously treating this very, very seriously." 

Anyone with information is urged to contact Crime Stoppers on 1800 333 000.