Teenager Mahmoud Hrouk was seen socialising with a group of boys in the hours before he was bashed to death in a vacant home used as a "local hangout" in western Sydney, police say.

Relatives found the 16-year-old's bloodied body in the Fairfield East house that has been used by local teenagers in the past three to five months.

Homicide Detective Inspector Grant Taylor said he believed a number of youths recently moved a lounge chair into the single-storey home on Belmore Street and were eager to speak to anyone who had seen anything.

"We are very interested if anyone can tell us who may have frequented that house and used it as hangout," he said.

"Some individuals have delivered a two- or three-seater lounge to that residence for use sometime in last month or so."

Inspector Taylor said Mahmoud's killer or killers possibly fled the mystery house and ran towards Seaman Avenue late on Saturday or the early hours of Sunday.

He also urged residents to check their gardens and bins just in case the teenager's killer or killers had dumped his mobile phone or other personal items nearby.

"We strongly believe that people who live within that area may have seen the deceased with others possibly of similar age or older and we are very keen for those members of the public to make contact with Crime Stoppers," he said.

The former Granville High School student was seen at Villawood McDonald's about 6.30pm on Saturday and then was seen at a number of streets surrounding the house where he was eventually killed.

His mother has said she last spoke to her son at 9.30pm before his phone cut out or his battery went flat.

Dozens of his family members searched the streets that night and found his Giant mountain bike on Melaleuca Street.

Yas Abooch said she was one of Mahmoud's aunts and she believed her nephew had been killed by a group of boys he knew.

"He got bashed to death apparently by a group of boys - most likely set up by his so-called mates," she posted on Facebook.

Police said they were considering the possibility Mahmoud was killed by more than one person but remained tight-lipped about why anyone would want him dead.

Inspector Taylor said they believed the deceased might have been at a number of different places on Mitchell, Melaleuca, Normandy, Bligh, Belmore and Tangerine Streets between 6.30pm and midnight on Saturday, May 16.

"We believe that the deceased remained in that area [Villawood and Fairfield East][  and was either on foot or on his bicycle or possibly at times in a vehicle going between those locations," he said.

"This was a brutal and vicious bashing. He was brutally assaulted in a very vicious and callous attack."

The police appeal for information comes after more than 500 mourners gathered at Lakemba Mosque on Wednesday, including his mother father and six siblings.

Mahmoud's Lebanese Muslim Association funeral was conducted at midday before his burial at Rookwood cemetery.

Phone Crime Stoppers, 1800 333 000, with any information.