Three young men tortured and killed a Sydney teenager over $500 cash before burying his body in a shallow grave in the Blue Mountains, detectives allege.

Alleged ring leader Yigit Erdogan, 19, and 18-year-olds Chris Hopkinson and Joel Robertson faced court today charged with the alleged kidnapping and murder of 17-year-old Justin Tsang.

Police believe the 17-year-old who was allegedly kidnapped in Sydney’s inner west pleaded for his life before he was murdered.

Sydney teenager Justin Tsang was allegedly tortured before he was murdered and buried by friends he met through an online game. (Supplied)

Late yesterday the three teenagers accused of the crimes were charged after Tsang's body was found buried in a shallow grave in the Blue Mountains on March 19.

The teenager went missing from Canada Bay earlier this month.

The fatal blow was made to Justin's head with a knife, Burwood Local Court heard.

Homicide squad commander Detective Superintendent Scott Cook says the victim was assaulted for hours.

(Left to right) Joel Robertson, 18, alleged ring leader Yigit Erdogan, 19, Chris Hopkinson, 18, faced court charged with the alleged kidnapping and murder of 17-year-old Tsang. (Supplied)

"There was some suggestion he was pleading for his life. It's very sad," he told reporters today.

His family had not heard from him for four days, and reported his disappearance on March 15.

Police believed his disappearance was suspicious and set up a homicide squad under codename Strike Force Liebert.

Det supt Cook said the motive appeared to be related to a dispute over property.

The three teens accused of the crimes were arrested after police raids overnight. (Supplied)

Police arrested a further man last night over the murder. (Supplied)

Court documents suggest Justin was kidnapped and assaulted with the intention of obtaining $500 cash.

"It's very concerning in a sense that if the underlying motive is a property dispute how can that escalate to torture," Det Supt Cook said.

"It really is disturbing."

Yesterday police arrested the three 18-year-old men and a 19-year-old man at Burwood Heights over his death.

Two of the 18-year-olds were charged with murder and take/detain person with intent to obtain advantage occasion actual bodily harm.

Three men allegedly assaulted Mr Tsang and then stabbed him to death, before burying his body. (Supplied)

Police allege Erdogan organised and coordinated the killing.

They say Erdogan - who was known Justin - picked him up from a Drummoyne house on March 11 in a BMW sedan.

It's understood he was the only one from the trio that knew Justin.

He was taken to the Burwood Heights house where the other men lived, held against his will and stabbed to death, it's alleged.

His body was buried in a shallow grave near Jamison Lookout at Wentworth Falls.

Yesterday police arrested three 18-year-old men and a 19-year-old man at Burwood Heights over his death. (Supplied)

It's believed the men who lived in the Burwood Heights house met each other through online gaming and the game 'Mount and Blade War Band'.

“We think the murder was to do with a property dispute – the gaming may or may not add some other aspect to it but it’s certainly not the cause of it,” said Commander Cook.

Hopkinson stood guard with a wrench during the murder, the Burwood court heard.

"The allegation against (Chris Hopkinson) is that he stood guard with a weapon and detained Mr Tsang when his two co-accused inflicted terrible injuries upon him, which resulted in the death of Mr Tsang," magistrate Lisa Stapleton said.

Hopkinson's lawyer, Ken Buckman, argued his client was afraid and intimidated by Erdogan, who'd allegedly handed him the wrench.

"He was a very scared young man," Mr Buckman said.

The lawyer said he had doubts over the reliability of the principal witness's account of his client's involvement.

But this was rejected by magistrate Stapleton who refused Hopkinson's bail application noting the witness's detailed account was corroborated by mobile phone records and CCTV.

"The murder of Mr Tsang shows extreme violence and abhorrent callousness," Ms Stapleton said.

Erdogan appeared at Bankstown Local Court on Thursday.

He didn't apply for bail and it was formally refused. He's due to reappear on May 23.

Hopkinson and Robertson - who hadn't applied for release - were both refused bail to reappear at Burwood Local Court on May 29.

Investigations continue.