(JTA) — New York City increased its police presence at synagogues and other locations in the wake of an attack on a Jerusalem synagogue that left four dead.

“The NYPD is following developments in Jerusalem closely and working with the FBI Joint Terrorism Task Force to monitor any further developments,” the city’s police commissioner, Bill Bratton, said in a statement. “As of now, there is no specific credible threat to New York City.”

Mayor Bill de Blasio asked New Yorkers to remain alert and report suspicious activity, WCBS-TV reported. He said that the NYPD is “in close contact with its liaison post in Israel.”

The FBI said in a statement that it is “aware of the situation” and was “working in close collaboration and cooperation with the appropriate Israeli allies and partners.”

In his statement, de Blasio said, “New York City stands in solidarity with Israel at this difficult time, and we hope and pray for a peaceful and secure future for all of its people.” The mayor said he was “horrified and heartbroken” by the attack.