An MTA bus driver shut the doors on a girl’s arm — then drove for several blocks and laughed afterward, according to a witness and photo.

The backpack-wearing victim can be seen in a now-viral photo standing with her right arm extended in between the doors of the S46 bus on Staten Island on Friday. The photo was taken by another bus rider.

According to a third rider, Paul Costello — who posted the photo to Facebook — the city driver aboard bus No. 7072 “closed the door on the arm of a student, drove four blocks and laughed at her afterwards.”

Costello wrote that the “disturbing” incident happened around 5:20 p.m. nearby IS 61 in Tompkinsville, prompting screams from fellow passengers.

The girl “was waving to her friend, and wasn’t fare-hopping from what I could tell,’’ the rider wrote. “Even if she was doing something wrong, this is still disturbing and not appropriate.

“The bus wasn’t very full, and I was at the back of the bus. By the time people were able to react and try and help her, the door had been opened. It was about a ten second ordeal, with a bunch of people screaming.”

Costello, 24, told The Post on Tuesday that he was listening to a podcast on his cellphone when he heard screaming.

“As soon as I noticed her arm, I also noticed that the bus had begun moving,” Costello said, adding, “Multiple people on the bus began screaming. Some ran to the front of the bus to get the driver’s attention.”

But the female driver ignored other riders’ calls to stop the bus, Costello said.

“Despite multiple passengers yelling at her to stop, she continued driving for far too long before stopping and opening the door,” the man said.

Costello noted that just before the driver opened the doors, one rider captured a photo of the stuck girl.

“The girl was obviously shaken, and the other passengers were yelling at the driver asking, ‘What’s wrong with you?’ ‘Why did you close the door on her like that?’ ” Costello said.

Costello added that he heard others say to the bus driver, “Why are you laughing?” and “Stop laughing.”

Following the incident, Costello — who got the photo from the rider who snapped it — sent the young girl the image “so that she could show her parents,” he said.

Costello then filed a complaint with the MTA regarding the incident.

The MTA said the bus driver has been suspended 10 days because of the incident.