The deadly Israel-Gaza conflict has heightened tensions in the U.S., with authorities nationwide warning of increased antisemitic and anti-Palestinian activity.

ABC News has confirmed that every major city police department in the U.S. is on a heightened state of alert monitoring the situation ahead of planned demonstrations Friday and into the weekend.

The Department of Homeland Security said it is monitoring events as they unfold in Israel and Gaza, urging faith and community leaders “to be alert, vigilant and prepared.”

Several instances of violence on Wednesday put New York law enforcement officials on high alert, responding with increased police presence in religious and cultural institutions.

Around 8 p.m. ET, police say a 34-year-old man was hit over the head with his own Palestinian flag during an anti-war protest in Williamsburg, Brooklyn.

A suspect wearing traditional Jewish attire drove up to him on a scooter, struck him with the vehicle and took the flag out of his hands, hitting him over the head multiple times with it, according to authorities.

The suspect fled on his scooter and is being sought, police say.

Also on Wednesday night, the NYPD reported that a 24-year-old Israeli man was struck with a wooden stick near Columbia University in Manhattan following an argument with a 19-year-old woman who was reportedly ripping down flyers in relation to the Israel-Gaza conflict.

Later that night, around 11:30 p.m. ET, authorities say an 18-year-old man was assaulted by one man in a group of men waving Israeli flags who jumped out of their vehicles in Bay Ridge, Brooklyn.

The men, who appeared in their 20s, had allegedly been driving around the neighborhood with their flags, yelling anti-Palestinian statements. According to authorities, the men asked the teen if he was Palestinian, to which he replied he was Egyptian but added “Free Palestine,” a popular slogan that calls attention to Israel’s policies in Palestinian territories.

A man allegedly kicked and punched the teen multiple times and harassed two others who were with him, ages 19 and 21. He fled the scene in the vehicle.

No arrests have been made, and the incident is being investigated by the NYPD as a possible bias crime.

Other incidents have been reported by local news outlets in Utah, Missouri and California.

Cultural and religious groups, including the New York Chapter of the Council on American-Islamic Relations Executive Director Afaf Nasher and the Bipartisan Congressional Caucus on Black-Jewish Relations, have condemned the actions.

Gallyamov worked for Putin when he was Russia's prime minister between 2008-12. Later, Gallyamov became an outspoken — and sometimes critical — political consultant and analyst, who moved his family to Israel in 2018 but continued to work in Russia.

Last spring, he learned he was on Russia's wanted list and would be arrested if he returned.

Gallyamov said he was surprised by Putin's one-sided reaction toward the attacks in Israel. He said he believes it shows that Russia has become an "Iran proxy, like Hamas itself or Hezbollah.

"Previously if you wanted to get Russia's position, you needed to negotiate with Russia. Now you've got to go to Tehran," Gallyamov said.

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