PHILADELPHIA -- A scary and disturbing trend has emerged with another SEPTA commuter being attacked and robbed over the weekend.

The third such attack in the past three weeks happened at 15th and Market on the Market-Frankford elevated line.

A SEPTA official said the authority is taking action, hoping to fast-track a security plan that would mean installing new surveillance cameras, call boxes and public address systems at all of its stations by 2011.

However, the same SEPTA official said that, due to the randomness of the attacks, they are crimes that are very difficult to prevent, NBC 10's Deanna Durante reported.

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Extra police from the city and transit agency along with the Guardian Angels are now keeping watch.

For some, it's enough.

"I like seeing the police around. It makes me feel much safer," said SEPTA rider Wajayha Abdullah.

For others, it's not enough. Asked if he's seeing more police on the SEPTA platforms or concourses, SEPTA rider Kevin Zuber said, "Not really. I'm down here almost every day going to work, back and forth. No, not really."

"You can have three cops in one area. The kids will keep moving until they get to a spot where there isn't a cop and just assault the next person who comes by," said SEPTA Public Safety Director Jim Jordan.

SEPTA said it is concerned over the latest attack Friday at about 11 p.m. on board a subway train between near 15th and Market streets.

Police said a 30-year-old man told them he was assaulted by a group of men wearing wigs. He reported being slapped and hit with an umbrella as the thugs stole cash from his pockets.

He spoke exclusively to NBC 10.

"One of them, with a wig on, was causing a disturbance on the train," said the victim, who declined to be identified. "I asked them if they could quiet down. At that point, they became irate.

"One of them started swinging an umbrella and hit me in the head with it. I just blocked (the umbrella) to protect myself -- I didn't fight back or anything -- but in the melee, a couple of them reached in my pockets and took the money in my pockets, which was about $43 or something like that."

Friday's victim escaped major injury, police said. He was treated for cuts and bruises. No arrests have been reported.

It was the latest in a round of attacks on unsuspecting riders.

On March 26, 36-year-old Sean Conroy died after a confrontation on a SEPTA concourse at 13th and Market streets. Five have been charged with murder in the case.

On April 3, a woman was targeted by a group of teens. She said she was beaten and robbed underground near Eighth and Market streets.

"I think it's very messed up that you can't ride around on public transportation without worrying about getting hurt by somebody," said SEPTA rider Bernard McDonald.

SEPTA said it's increasing its patrols by offering officers overtime in an attempt to get 30 more officers on patrol during peak hours from 2 p.m. to 5 p.m. in the afternoon and hopes to have 1,000 security cameras installed in the next few years in SEPTA stations.

There are also plans to install cameras on subway trains.

"It's a very opportunistic crime. It's not planned. It doesn't necessarily have a motive. And that type of crime is very hard to prevent," Jordan said.

NBC 10 reported that the attacks have not been related. Anyone with information on Friday's robbery is asked to call Philadelphia police.