SYDNEY: A Muslim couple racially abused by a Sydney train passenger have thanked another commuter who defended them, with a video capturing the incident going viral on social media as police launched an investigation.

The pair, Hafeez Ahmed Bhatti and Khalida Hafeez, were riding on the airport-bound train on Wednesday when a woman sitting nearby started to rant at them, the person who recorded the footage said.

"The lady next to me was saying things like 'all the people that were dying were because of the Muslims in the world and look what's happening overseas'", Stacey Eden, reported to be in her early 20s, told the Australian Broadcasting Corporation on Friday.

Eden said the woman added: "Read the newspapers, why are you following this religion for, why do you wear things like that so you can marry a man who's going to go marry a six-year-old? I was like, 'this isn't right, why are you saying these kinds of things?'"

Eden is heard replying to the woman on the video, which she posted on Facebook: "She wears them for herself, OK? She wears them because she wants to be modest with her body".

Bhatti shared Eden's clip on his Facebook page on Thursday, writing: "This video was not recorded by me. But that is what happened to us on sydney train, God bless Stacey Eden who supported us".

"I was a little shocked, she touched my wife's head like she was blessing although no one likes a stranger to touch them and then she started her ignorant comments," Bhatti added.

Other commentators on his post also praised Eden for speaking out.

"Thanks to this lady (Stacey) who came from nowhere as an angel," one user wrote.

Another added: "Great work by Stacey, good job by you as well for being patient and tolerant. The old lady should be ashamed for passing biased comments without knowing the reality".

The footage has attracted more than 130,000 views on YouTube, more than 750,000 views on Facebook and was shared more than 10,000 times on the social networking site since it was uploaded on Wednesday evening.

In the footage, the woman can also be heard mentioning Martin Place, which is near a central Sydney cafe where a lone gunman inspired by the Islamic State (IS) group took customers and staff hostage in December. Two people, and the gunman, were killed in the stand-off.

"That's not her doing it, that's a minority of people, not a majority of people, OK... have some respect," Eden told her.

New South Wales police told AFP that they were aware of the allegations and had been in touch with Eden.

"An investigation is now underway into the incident," the spokesman added.

There have been several videos of racial abuse on Australian public transport that have gone viral online. In July a 55-year-old woman was given a good behaviour bond after verbally abusing an Asian passenger on a Sydney train journey in a rant that was captured on video.

In 2012 a French-speaking woman singing on a Melbourne bus was told by a man to “speak English or die” in another viral video. Two Chinese students were burned, beaten and racially abused on a Sydney train the same year.