Terrorists used meat cleavers to kill four men in Tuesday's attack on a synagogue in Jerusalem. Photo: IDF Spokesperson Peter Lerner.

Mayor Bill de Blasio said on Tuesday that New York City will boost the defenses of religious targets following the slaying of three American rabbis by a Palestinian terrorist in an attack at a Jerusalem synagogue.

“The NYPD is in close contact with its liaison post in Israel. We have increased our police presence at synagogues and other key locations around the city,” de Blasio said in a statement. “As always, we ask New Yorkers to stay alert and immediately report any suspicious activity.”

Tuesday morning’s synagogue attack claimed the lives of rabbis Moshe Twersky, Arye Kupinsky and Kalmen Levin, along with British-born Avraham Shmuel Goldberg and Zidan Sayif, a Druze Israeli police officer who was the first on the scene. Terrorists used a pistol, knives and meat cleavers to slaughter the men, who were attending morning prayers at the synagogue in Jerusalem’s Har Nof neighborhood . The terrorists injured another six people before being shot dead by security personnel.

De Blasio said he was “horrified and heartbroken” by the attack.

“My thoughts and prayers are with the victims’ families,” he added. “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.”Ž”

New York City Governor Andrew Cuomo released a separate statement on Tuesday saying he was “deeply saddened” by the incident.

“This attack was a deplorable act of evil that should be denounced as such by all – regardless of their political or religious beliefs,” he said. “I want to reiterate that friends stand together in times of crisis. Today New York joins with all of Israel as they mourn those that were lost. We stand shoulder to shoulder with our Israeli friends.”