Several people were stabbed at a Jewish place of worship in upstate New York on Saturday night.
"At 9.50 this eve, a call came in about a mass stabbing ... It's the house of a Hasidic Rabbi. Five patients with stab wounds, all Hasidic, were transported to local hospitals," the Orthodox Jewish Public Affairs Council tweeted.
Two people were reported to be in critical condition, the council said.
CBS New York said that the attacker was armed with a machete when he went into the rabbi's property in Monsey, New York State, an area with a large Jewish population, during a Hanukkah celebration and stabbed at least three people before fleeing.
Yossi Gestetner, a co-founder of the council for the Hudson Valley region, told the New York Times that one of the victims was the rabbi's son.
"The house had many dozens of people in there," Gestetner said.
Police in the United States have battled a spate of attacks against Jewish targets in recent years.
Saturday's stabbing follows a shooting earlier this month at a kosher deli in a New York suburb that authorities said was inspired in part by anti-Semitism.
Six people were killed in the Jersey City shooting, including the two attackers.
A report in April from the Anti-Defamation League said that the number of anti-Semitic attacks in 2018 was close to the record of 2017, with 1,879 incidents.
In response to the recent surge in hate-crimes in New York, Mayor Bill de Blasio announced on Friday that the NYPD was stepping up patrols in three districts and increasing the number of visits to houses of worship.
After Saturday's attack, the mayor also tweeted that he had recently spoken to Jewish friends who are fearful of outwardly showing their faith.
"We will NOT allow this to become the new normal," he wrote. "We'll use every tool we have to stop these attacks once and for all."
But Mr de Blasio's commitments have not yet eased fears of further persecution - either in the United States or around the world.
In Israel, President Reuven Rivlin expressed his "shock and outrage" at the attack.
"The rise of anti-Semitism is not just a Jewish problem, and certainly not just the State of Israel's problem," he said.
"We must work together to confront this evil, which is raising its head again and is a genuine threat around the world."
In the US, Jonathan Greenblatt, national director of the ADL, called on authorities to increase protection for the Jewish community.