PENNSYLVANIA (REUTERS) - The rape of a woman aboard a Philadelphia subway witnessed by as many as 10 passengers, some of whom appeared to film the attack, could have been stopped quickly if one had called 911, police said on Tuesday (Oct 19).

The woman was raped shortly after 9pm on Oct 13 on a train run by Southeastern Pennsylvania Transportation Authority (SEPTA), which provides public transportation in Philadelphia, SEPTA Transit Police Chief Thomas Nestel III said.

"As many as 10 people actually saw some part of the attack on this rider," Nestel said on Philadelphia radio station WPHT.

Describing police review of surveillance video, Nestel said, "We were watching to see if somebody put a phone up to their ear indicating they might be calling 911. Instead, what we saw was people holding their phone up as if they were recording or taking pictures."

"It may have been stopped sooner if a rider called 911," SEPTA spokesman John Golden said in a statement, referring to the US phone number for emergency services.

SEPTA and the Upper Darby Police Department, which is investigating the incident, did not immediately confirm other details of the incident reported by local media.

Surveillance video from the train car showed the woman attempted to rebuff her attacker, repeatedly pushing him away as he initially groped her and ultimately sexually assaulted her, local media reported.

One person finally alerted 911. It was that call by an off-duty SEPTA employee that quickly brought transit police onboard, allowing them to stop the assault and arrest the alleged rapist, SEPTA police said.

"He was on top of our victim and committing the assault when they entered the train," Nestel said.

Women's rights advocates said the failure of bystanders to call 911 was "despicable" and disturbing.

"My greatest fear about it is two-fold: One is that people just don't care and the other is that they thought this might have been consensual sexual activity, and that's what rape looked like to them," said Carol Tracy, executive director of the Women's Law Project in Philadelphia.

Fiston Ngoy, 35, faces charges of rape, involuntary deviate sexual intercourse, sexual assault and other offences, local media reported. Ngoy, who listed his address as a homeless shelter in Philadelphia, was held on US$18,000 bail and was scheduled for an Oct 25 court hearing, local media reported.

Ngoy claims the encounter was consensual, but the woman denies that, local media reported.