An attacker stabbed five people late on Saturday at a Hasidic rabbi's home in New York state before fleeing, a Jewish organization said, a rampage that came after days of increased tensions over anti-Semitic assaults.

The Orthodox Jewish Public Affairs Council (OJPAC) said on Twitter an attacker wearing a scarf stabbed the victims at a house in Monsey, Rockland County, about 30 miles north of New York City.

All five victims were taken to local hospitals, the council said, adding that two of the victims were critical, with one of them stabbed at least six times.

The attacker fled in a gray Nissan Sentra, according to the OJPAC. Local media reports said police were searching the area for the assailant. The Ramapo Police Department did not immediately comment on the situation.

An OJPAC official, Yossi Gestetner, told The New York Times the attack happened at around 10 pm during a Hanukkah celebration that was being attended by many dozens of people at the rabbi's home.

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About a third of the population of Rockland County is Jewish, including a large enclave of Orthodox Jews who live in secluded communities.

New York Attorney General Letitia James said she was "deeply disturbed" by the events in Monsey.

"There is zero tolerance for acts of hate of any kind and we will continue to monitor this horrific situation," she said in a Twitter post.

New York City's police department said on Friday its officers were stepping up patrols in heavily Jewish neighbourhoods following a spate of anti-Semitic attacks.

"Hate doesn't have a home in our city," Mayor Bill de Blasio wrote on Twitter on Friday, calling the assaults attacks on all New Yorkers.

In more deadly recent attacks, a gunman killed a female rabbi and wounded three other people during Sabbath services at Congregation Chabad in Poway, near San Diego, on the last day of Passover in April 2019.

Six months before that, a gunman killed 11 worshipers at the Tree of Life synagogue in Pittsburgh in the deadliest anti-Semitic attack in US history.

The Jewish holiday of Hanukkah commemorates the 2nd century BC victory of Judah Maccabee and his followers in a revolt against armies of the Seleucid Empire.