Hanukkah celebrations have been marred by anti-Semitic attacks in New York and London.

Key points: Five people have been stabbed in a Hasidic rabbi's home in New York state

Five people have been stabbed in a Hasidic rabbi's home in New York state New York's Governor has labelled the attacks "domestic terrorism"

New York's Governor has labelled the attacks "domestic terrorism" A local MP has called London's graffiti attack "unbelievable" and "senseless"

In New York state, an assailant burst into a party at a Hasidic rabbi's home and stabbed five people, while graffiti was daubed across a synagogue and shopfronts in north London, referencing a debunked conspiracy theory implicating Jews in the 9/11 terror attacks.

New York state Governor Andrew Cuomo met with victims who had been attending the Hanukkah celebration at the home of rabbi Chaim Rottenberg on Sunday.

"This is terrorism, it is domestic terrorism," Mr Cuomo told reporters.

"These are people who intend to create mass harm, mass violence, generate fear based on race, colour, creed."

Rabbi Rottenberg's home is located in a New York state county where a third of its population is Jewish. ( AP: Allyse Pulliam )

The stabbings happened about 10:00pm on Saturday (local time) at the home of Rabbi Rottenberg, located next door to his Congregation Netzach Yisroel synagogue.

The incident left one person critically wounded while the rabbi's son was also injured, Governor Cuomo said.

The suspect was arrested and named as Grafton E Thomas, who was charged on Sunday morning with five counts of attempted murder and one count of burglary.

He pleaded not guilty. Bail was set at $US5 million.

Grafton Thomas (right) was arrested 48 kilometres from the scene in New York City. ( AP: Julius Constantine Motal )

Police said a witness saw the suspect fleeing in a car and alerted police to the licence plate number.

They entered that information into a database and used plate reader technology to track the vehicle to Manhattan in New York City, where the suspect was arrested.

Authorities were yet to provide a motive.

'We didn't have time to react'

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Aron Kohn, 65, told The New York Times he was inside the residence during the stabbings.

"I was praying for my life," Mr Kohn, said.

"He started attacking people right away as soon as he came in the door. We didn't have time to react at all."

Hanukkah, Hebrew for "dedication", commemorates the 2nd-century BC victory of Judah Maccabee and his followers in a revolt in Judea against armies of the Seleucid Empire and the ensuing restoration of the Jewish temple in Jerusalem.

Light is a main theme of the eight-day festival because the Maccabees found only enough ritually pure oil to fuel the temple's ceremonial lamp, The Menorah, for one day, but it burned for eight days, according to Jewish lore.

Rabbi Rottenberg's home is located in Monsey, Rockland County, about 48 kilometres north of New York City.

A third of the county's population is Jewish, including a large enclave of Orthodox Jews who live in secluded communities.

Spike in anti-Semitic activity

Orthodox Jewish men speak to police following the stabbing. ( AP: Allyse Pulliam )

The attack was the latest in a string of violence targeting Jews in the region, including a December 10 massacre at a kosher grocery store in New Jersey.

Last month in Monsey, a man was stabbed while walking to a synagogue.

Mr Cuomo said the stabbing was the 13th anti-Semitic attack in New York since December 8 and endemic of "an American cancer on the body politic".

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CNN also claimed there was an attack on Jewish New Yorkers every day last week.

The attack on the party, which was attended by dozens of people, followed a spate of anti-Semitic attacks in New York City and surrounding areas.

New York City's police department said on Friday its officers were stepping up patrols in heavily Jewish neighbourhoods in response.

In more deadly recent attacks, a gunman killed a female rabbi and wounded three people during Sabbath services in San Diego in April, while a gunman shot and killed 11 worshipers at a Pittsburgh synagogue in October 2018.

The attack and the recent wave of anti-Semitic violence in the region drew condemnation from various high-profile leaders.

"Israel unequivocally condemns the recent expressions of anti-Semitism and the vicious attack in the middle of Hanukkah on the rabbi's house in Monsey, New York," Prime Minister Benjamin Netanyahu said.

Democratic Congress House Speaker Nancy Pelosi said on Twitter she was, "deeply disturbed by the stabbing in Monsey and the many recent anti-Semitic attacks in the NY metro area, especially during this holiday season".

"We must condemn and confront anti-Semitism and all forms of bigotry and hate wherever and whenever we see them," Ms Pelosi said.

London attack references anti-Semitic conspiracy theory

London's police service are investigating the racially motivated hate crime. ( Twitter: Oliver Cooper )

In London, the Star of David and the numbers "9 11" were sprayed on a synagogue and several shops in Hampstead and Belsize Park, in the north of the capital.

The graffiti referenced an anti-Semitic conspiracy theory related to the US's September 11, 2001 terror attacks which falsely claims Jews were responsible for the attacks.

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Local MP for Hampstead and Kilburn Tulip Siddiq tweeted that the graffiti was, "Unbelievable, senseless, disgusting anti-Semitism at the heart of our community".

"We must all stay vigilant in order to continue the fight against this hatred," she wrote.

London police said they were investigating the racially motivated hate crime after being informed on Saturday night. They said no arrests had been made.

The Board of Deputies of British Jews wrote on Twitter: "This is a reminder that antisemitism is still with us.

"We hope action is taken to find and punish the perpetrators. Let's all work to defeat antisemitism in 2020."

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