More than 400 teenagers laid siege on a lakeside park in upstate New York during back-to-back broad daylight “teen takeovers” — prompting security increases ahead of Memorial Day Weekend.

Horrified parents and young children fled the Ontario Beach Park in Rochester on Sunday as a mob teeming with hundreds of unruly youths flooded the parking lot, WHAM reported.

The brawlers milled around the parking lot and appeared to throw punches at random as several full-on fights broke out.

Crowds gathered around each fistfight all while bystanders carefully steered their cars through the parking to reach an exit that wasn’t blocked by the hooligans.

Several teens were thrown onto the concrete and jumped on. Others were slammed against parked vehicles as the aggressors continued to wail on them, according to video footage obtained by WHEC.

Hours earlier, several brawling teenagers were ejected from the city’s annual Lilac Festival at Highland Park — just 18 miles away from Ontario Beach., WHEC reported.

The mob returned to Ontario Beach Park on Monday and started clashing again. Both throngs appeared to begin the night at the park’s gazebo before inevitably spilling over into the parking lot, according to footage obtained by WHAM.

One person was arrested during the scuffle at the Lilac Festival, but no one was cuffed at Ontario Beach Park on either day, according to the Rochester Police Department.

Rochester Mayor Malik Evans said at a Tuesday press conference that both takeovers were meticulously planned on social media down to an exact meetup time.

“We look at the post and they arrange to go up and fight, and then they want to take their phone out and they want to be cool, and then they want to push it to social media. And then you have people that pick it up,” Evans said.

“Meanwhile, they’re not showing the kids that are out playing basketball. They’re showing the kids that are coming to the beach to try to wreak havoc because they want to become social media famous. That’s what this is about.”

The Rochester Police Department initially increased its patrols at the park when “teen takeovers” started cropping up in 2020. The department said it would be partnering with the Monroe County Sheriff’s Office and New York State Police to monitor the park over Memorial Day Weekend.

“We’re gonna be out here, there’s gonna be a lot of police out here, a lot of law enforcement, and if you see anything that you’re concerned about it, please let us know, because we can’t see everything,” Rochester Police Captain Nate Cornell said.

Cities countrywide are trying to combat the relentless “teen takeovers.”

In Washigton, DC, federal prosecutors are leading efforts to charge rabble-rousing teens — and their parents.

“We’re coming for you and we’re coming for your parents,” US Attorney Jeanine Pirro declared.