Cops prevented a raging mob of Harlem locals from attacking a maniac accused of slashing an 11-year-old girl in the head on a Manhattan subway platform Friday afternoon moments after he pummeled a woman in the streets nearby, police and law enforcement sources said.

The fiend allegedly punched the unsuspecting 43-year-old woman around 2:15 p.m. on East 115 Street and Park Avenue in East Harlem, according to sources.

He then fled to the 116th Street 6 subway train where he preyed on the girl — knifing her in the back of the head and cutting her ear as she stood on a downtown platform with her mom, sources said. 

A UPS worker said the young victim was “scared and crying” while she was being treated by medics near a juice bar.

“Her head was really sliced,” he added.

Photos obtained by The Post shows one of the blood-soaked victims sobbing as she’s gurneyed into the back of an ambulance. 

Wild video posted on social media shows the moment the accused attacker is surrounded by cops as the outraged mob tries to mete out street justice. 

In the clip, one man appears to poke him with a cane as the alleged assailant cowers behind cops.

“Back up!” police shout at the crowd. 

“You f—–g piece of s–t!” one man yells. 

“Don’t let him go!” says another man as police hold back the bloodthirsty mob. 

Cops finally took the 30-year-old suspect into custody, who sources say has more than 20 prior arrests.

Charges were pending against him Friday night.