Protesters were caught on video vandalizing three NYPD vans on Manhattan’s Lower East Side, slashing their tires, spray-painting graffiti and damaging windows, police said Monday.

Video released by cops shows one man pounding on the window of an unoccupied police van with a pole from a sign he was carrying on Essex St. near Rivington St. about 10 p.m. Saturday, officials said.

“FTP,” which stands for f— the police, can be seen scrawled on the same van — and two other men appear to be scrawling the same message on a van in the background.

Anyone with information about the vandalism is asked to call Crime Stoppers at (800) 577-TIPS. All calls will be kept confidential.