The violent beating of three older men captured on video in San Francisco’s Chinatown over the weekend has sparked fear and outrage among some residents in the city’s Chinese-American community, who said they feel increasingly targeted following several high-profile attacks on the neighborhood’s most vulnerable residents.

A citizen captured the disturbing video of the attack from an overhead perch, showing four assailants ambushing a group at Clay Street and Walter U. Lum Place on the southwest corner of Portsmouth Square just after 9 p.m. Saturday.

Officials said the violence erupted after one of the attackers ripped the cell phone from a man’s hand and others tried to intervene only to be pummeled.

One assailant cold-cocked a man with a sweeping roundhouse punch, leaving him unconscious on his back as others struggled in the street feet away. The marauders then jumped into a waiting sport utility vehicle and sped off.

Three victims, all men ages 63, 67 and 68, were left with varying injuries, police said. Two were treated at San Francisco General Hospital and later released. A third was checked out by paramedics and released at the scene.

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Wilma Pang, who calls herself “the unofficial mayor of Portsmouth Square” and recently ran for mayor, said the victims had been playing cards in the park before the attack.

“It seems like they were targeting seniors because they can’t resist as easily,” she said.

No one has been arrested and no suspects have been identified in the attack. Supervisor Aaron Peskin, whose district includes Chinatown, visited the scene on Monday and said police believe the same vehicle in the attack was involved in another robbery the day before.

In that case, a man violently wrestled a woman’s purse away from her outside the Garden Bakery on Jackson Street. He then jumped into an SUV matching the description from Saturday’s incident and disappeared.

“In almost 20 years on and off the board of supervisors, I’ve never seen violence like this in District Three, particularly in the senior-filled community of Chinatown,” Peskin said. “I am more than concerned about it.”

The police department has “saturated” the area with officers as investigators work to track down the group, Peskin said.

“We do not tolerate this violence in San Francisco,” he said. “We’re going to apprehend these criminals.”

The weekend violence has ignited frustration from residents in Chinatown, following other recent disturbing incidents. Last month police arrested 19-year-old Deshawn Pierson — one of three suspects in a violent July attack on two residents at Stockton and Pacific streets.

In that case, Pierson and two others, who have not been arrested, allegedly threw a 56-year-old man onto the ground and knocked out a 69-year-old man who tried to help. During the assault, the group stole a Rolex watch from the first victim, police said. The victims have since recovered.

And on New Year’s Eve, 26-year-old Teandre Howard-Kidd was accused of sexually assaulting a 99-year-old woman in her apartment in Chinatown’s Ping Yuen housing project.

Norman Fong, Executive Director of the Chinatown Community Development Center, which oversees the complex, said the violence is “getting too much for our community.”

“The question is, why are young people picking on our seniors? Easy prey is most often the answer but the impact is more than that,” Fong said Monday. “You don’t have to punch out a senior.”

Fong said the attacks are reminiscent of 2010 when the Bay Area was shaken by a number of attacks on Chinese-American seniors.

On Monday, Sasanna Yee held a demonstration for “love, peace and unity,” sitting in the center of the square and meditating with two young men. “We are saying no more in silence,” a sign next to them read.

Yee’s 89-year-old grandmother, Yik Oi Huang, was brutally assaulted on Jan. 8 in the city’s Visitacion Valley and suffered a broken neck, skull and arms and lost teeth. Yik is now in long-term care at Laguna Honda Hospital where “she will never recover,” Yee’s friend, Josephine Zhao, said.

“The severity and brutality of these incidents is continuing to escalate and it’s bringing shame to our city,” Zhao said.

Evan Sernoffsky is a San Francisco Chronicle staff writer. Email: esernoffsky@sfchronicle.com Twitter: @EvanSernoffsky