The NYPD said Tuesday that it has increased attention to synagogues and is working with other law-enforcement agencies after a deadly attack at a Jerusalem synagogue in which four people -- including three Americans -- were killed.

In a statement, Police Commissioner William Bratton said his department is "following developments in Jerusalem closely and working with the FBI Joint Terrorism Task Force" to monitor developments.

The statement also said there is "no specific credible threat to New York City."

Two Palestinians armed with a meat cleaver and a gun killed four worshippers in a Jerusalem synagogue on Tuesday before being shot dead by police, the deadliest such incident in six years in the holy city, Reuters reported.

"I am horrified and heartbroken by today's terror attack in Jerusalem," Mayor Bill de Blasio said in a statement expressing solidarity with Israel.

Sen. Charles Schumer (D-N.Y.), also in a statement, called the killings "outrageous" and criticized the actions of Mahmoud Abbas, the president of the Palestinian Authority.

Schumer said the killings are a "reckless incitement, not only of Hamas, but of Mr. Abbas and the Palestinian Authority; they are co-conspirators in the murder of these four religious teachers and rabbis. Their dishonest inciting of Palestinians is resulting in the death of innocent people, and it must stop."

Abbas had condemned the attack, Reuters reported. "The presidency condemns the attack on Jewish worshippers in one of their places of prayer in West Jerusalem and condemns the killing of civilians no matter who is doing it," his office said in a statement to Reuters.