These latest attacks have subway riders worried about safety.
As CBS2's Jenna DeAngelis reports, one of the incidents happened at Columbus Circle.
Police say the victim was stabbed in the eye, among at least five people hurt on the subway system Friday morning. Police believe the same group is responsible for all of the attacks.
"Here you have the amount of damage that can be done in a half hour by a number of people," said NYPD Commissioner Dermot Shea.
It started at about 4:20 a.m. Friday. Police say a 44-year-old man was on a southbound 4 train when three to five male suspects approached him and slashed him on the cheek.
The victim got off at the Union Square station, but the suspects stayed on the train.
Five minutes later, they allegedly slashed one man and punched another.
Five minutes after that, near Brooklyn Bridge station, they allegedly slashed a fourth man in the head. Police say they took his wallet and cell phone.
"The victims described two, three, four, upwards of five males. It looks like they were pairing off as the train was moving down along the 4 line," an NYPD official said.
WATCH: NYPD Officials Discuss Arrest Of Slashing Suspects
As CBS2's Jessica Layton reports, just before 11:30 a.m., officers recognized the four teenage suspects near 79th and Broadway and handcuffed them.
None of the victims have life-threatening injuries.
Police say the MTA cameras helped identify the four suspects.
The MTA was quick to thank the NYPD for the rapid arrests but has complained police aren't doing enough.
"Makes me scared to just even take the train, that's the crazy thing," said commuter Chris Methura.
Some commuters share that concern. Others say they still feel safe riding the subway, but all DeAngelis spoke to have heightened awareness.
"It has me pay attention to my surroundings a little bit more, I see it more as a wake up call. Be aware," said East Village resident Ruth McCullough.
"There's no other viable way of really getting around, so we're just sort of hoping it improves," said Greenpoint resident Mark Chin.
The MTA says in its latest survey, 75% of customers say their first priority concern is crime. Most want to see more cops on platforms and in subway cars.
Watch Jenna DeAngelis' report
"We've been loud and clear about what we need, pressing the mayor and the city for months for additional resources, full time uniformed police officers and mental health resources in the subway," said MTA Chairman Pat Foye.
Foye is calling for more NYPD officers. Shea announced 600 more were deployed Thursday.
"This is primarily a responsibility of NYPD but, having said that, we've added 100 MTA officers to the system," Foye said.
The president of the Transit Workers Union counted 15 instances of assault with razors and knives since Sunday. His union members are among those hurt, and he's calling out Mayor Bill de Blasio.
"He's got blood on his hands," said Tony Utano, TWU Local 100 president. "Why don't you just resign?"
"You got six more months to go, and you don't care. So give it to someone who cares and is gonna do the right thing," he added.
De Blasio press secretary in a statement said the city has pulled cops off desk duty and put them on platforms and trains.
"New York City is surging over 500 officers on top of a 2,500-strong transit force to fight subway crime. The City has pulled cops off desk duty and put them on platforms and trains. We're going to keep putting massive resources into this fight to keep our subways safe. Meanwhile the MTA sends out statements that point fingers and talk about mayoral politics. Get with the program, help us fight back this crime," Bill Neidhardt wrote.
Still, the group Passengers United has a message for commuters: ride at your own risk.
"Have a plan of safety. don't keep any valuables on you while you're on the subway. Don't display expensive phones, iPads," said Charlton DeSouza, president of Passengers United. "Obviously, we have a crisis."
This is all happening right before the MTA's planned date to return the subways to 24-hour service on Monday.
Friday morning's incidents follow four random attacks in the subway system on Wednesday.
CBS2's Jessica Layton contributed to this report.
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