Police saw girl trying to escape down nearby street at 1.30am Thursday

A girl who was allegedly held captive by an asylum seeker for a month in his Sydney home has been found after she was seen running barefoot for her life down a Western Sydney street.

The 15-year-old foster-home girl was allegedly kept as a hostage in a Blacktown home, in Sydney's west, for four weeks before she was seen by police being chased down a nearby street at 1.30am on Thursday.

An asylum seeker who came to Australia illegally by boat in 2013 is alleged to have been her captor, The Daily Telegraph reports.

Bangladeshi national Rashadul Islam, 29, was reportedly seen chasing the 15-year-old girl down the busy road before attempting to grab her and drag her away before police intervened.

Neighbour Amarjeet Singh told the Daily Telegraph the girl 'seemed scared and was asking police to help her' as she ran down the street.

'Across the road was a man in his late 20s talking to police and shouting at the girl,' Amarjeet said.

A man has been accused of holding a teenage girl hostage for a month at a home in Sydney's west where he sexually assaulted her (stock image)

The home (pictured) where Islam is alleged to have held the girl - who he claimed was his girlfriend - against her will for four weeks

When police saw the horrific scene unfold, the girl and her alleged captor were both taken back to Blacktown Police Station.

The girl was later taken to The Children's Hospital at Westmead for medical assessment, and was released a short time later.

She told police she had been sexually assaulted by Islam and kept against her will in the closed up house for four weeks.

The owner of the Blacktown house, Joe Chen, said Islam told him the 15-year-old girl was his girlfriend.

The 15-year-old girl was found at 1.30am on Thursday when police spotted her running along a Blacktown street, allegedly being chased by a man

'He said she was a girlfriend. (I) saw them together making dinner … shopping together, always together,' Mr Chen told The Saturday Telegraph.

The home owner said he rented the room to Islam two months ago and noticed the girl when she started living there three weeks ago.

Mr Chen also revealed Islam had a lock on his bedroom door.

The 15-year-old girl was reported missing by the foster home facility where she lived immediately after she went missing in October.

She reportedly met Islam in a chance encounter after leaving the group foster home in Sydney's west last month.

The Saturday Telegraph reported Islam arrived illegally by boat on March 24, 2013.

He landed in waters off Christmas Island and was held in a Phosphate Hill detention centre for two months.

He was then flown to Australia on May 15, 2013 where he was granted a bridging visa under the Rudd government.

The man has been charged with aggravated sexual assault and common assault- He was refused bail and is set to appear at Blacktown Local Court (pictured) on Friday

A crime scene was established at the address where police seized a number of items that will undergo forensic examination.

Islam, 29, has been charged with aggravated sexual assault and common assault and has been refused bail.

Detectives from the State Crime Command's Child Abuse Squad are investigating the matter and the Department of Immigration and Border Protection has been notified regarding the man's arrest.