A teenage boy has been charged with sexual assault following an alleged gang rape in western Sydney.

A 14-year-old girl was walking home from her friend’s house on Saturday night when she was attacked in a park at Doonside in Sydney’s west.

Police said a man approached the girl in Bill Colbourne Park at 11pm, forced her to the ground and sexually assaulted her.

The man’s five friends then allegedly took turns in an assault lasting 30 minutes.

Police confirmed on Thursday night a 16-year-old had presented himself to Blacktown police station.

He was charged with one count of sexual assault.

The teen was refused bail to appear in court on Friday.

The arrest came as police and African and Pacific Islander community leaders took part in a unity walk through Blacktown on Thursday night.

With social media feeding fears of reprisals there were concerns racial tensions would boil over between two ethnic groups.

The victim is believed to have a Pacific Islander background while the alleged offenders are described as African in appearance.

Asked about reported social media comments signalling reprisal violence, Blacktown police Superintendent Gary Merryweather confirmed on Thursday police were keeping an eye on it.

“There is a lot of hearsay conversations running around through electronic communications that happen these days,” he told AAP.

“Police are aware, we can’t say we are aware of everything, but we are being vigilant in that area.”

Police were also increasing patrols in Blacktown, Doonside and on trains, he added.

Supt Merryweather said everyone was upset about the attack and the tensions existed because of “the crime not because of the race”.

Sudanese community figure John Kon said he was not aware of any tensions, except on social media.

“…in the way this issue has been publicised on Facebook and other social media,” he said.

“It has been divided into an African and Pacific Islander’s problem but we as a community don’t have such a problem.

“Criminal are criminals and have to be treated as criminals.”

The gang rape occurred while the 14-year-old was walking home from a friend’s house through Bill Colbourne Reserve just before midnight.

Supt Merryweather said the victim was very traumatised and was being supported by family and friends.