The man accused of a stabbing spree at a New York rabbi's suburban home during Hanukkah was hit Friday with additional charges including a sixth count of attempted murder, a district attorney said.

Grafton Thomas, 37, allegedly entered the property in the town of Monsey during celebrations for the Jewish festival, knifing several people with a machete before fleeing.

Celebrants were forced to defend themselves by throwing furniture, and one of the injured, 72-year-old Josef Neumann who was hit in the head, remains in critical condition.

Thomas was initially accused of five counts of attempted murder.

In addition, he stands charged with three counts of assault, three counts of attempted assault and two counts of burglary, according to a statement from the district attorney of Rockland County, which includes Monsey, located some 30 miles (50 kilometers) from New York city.

He faces a maximum of 25 years in state prison over the charges.

US authorities have also laid federal hate crimes charges against Thomas who had expressed anti-Semitic views, referred to "Nazi culture" and drew swastikas in handwritten journals, according to a criminal complaint filed with a United States court.

According to US media, police are also investigating the possibility that Thomas was behind a separate attack on an Orthodox Jewish community on November 20 in Ramapo, also in Rockland County.

However police in the town have not confirmed the reports.

Thomas pleaded not guilty when he appeared for the first time in court on Sunday. His family and lawyer said he was mentally ill and had been hospitalized several times.

Rockland has the largest Jewish population per capita of any US county, with 31.4 percent, or 90,000 Jewish residents.

The attack on Monsey, home to a large Orthodox Jewish community, has heightened fears among American Jews, who have faced an increasing number of anti-Semitic attacks in recent years, particularly in the New York area.

The mayor and governor of New York have announced a series of measures, including an intensified police presence in Jewish communities, while US President Donald Trump has called to "eradicate the evil scourge of anti-Semitism."