Israel-Gaza conflict stokes tensions as violent incidents arise in the U.S.

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.