A violent and bloody attack has left four dead inside a Jerusalem synagogue and around six people were wounded. Orchestrated by a pair of Palestinians, the attack further deteriorated the strained relationship between Israel and Palestine, with Prime Minister Benjamin Netanyahu saying retaliation will be equal in measure.

The attack took place Thursday morning at the Kehilat Yaakov synagogue in Jerusalem, according to the Times of Israel. The two Palestinian men entered the religious building during prayers wielding a gun, meat cleaver and ax. After attacking worshippers, they exchanged gunfire with police, who ultimately killed them. Six others, including two police officers, were injured.

Netanyahu blamed the incident on Hamas, and Palestinian President Mahmoud Abbas and vowed to respond in kind.

“This is the direct result of the incitement led by Hamas and Abu Mazen,” he said, referring to Abbas. “Incitement that the international community irresponsibly ignores. ... We will respond with a strong hand to the cruel murder of Jews who came to pray and were caught by dark murderous hands.”

In response, the Abbas released a statement condemning the attacks, according to the BBC.

"The presidency condemns the attack on Jewish worshippers in their place of prayer and condemns the killing of civilians no matter who is doing it,” the statement said.

The four killed have been identified as Rabbi Moshe Twersky, 59, head of the seminary, Arieh Kupinsky, 43, Kalman Levine, 55, and Avraham Goldberg, 68.

NBC News has identified Twersky, Kupinsky and Levine as American citizens. The State Department has also said three Americans are involved but did not provide names. Goldberg is a British citizen. They all also hold Israeli citizenship.

According to Reuters, Palestinian media has identified the perpetrators as Ghassan and Udai Abu Jamal, and the Popular Front for the Liberation of Palestine claimed responsibility for the attack, which Israeli police have called a terrorist attack. The Palestinian group called the attack revenge after a Palestinian man was found hanged inside a bus. Authorities, however, believe the man committed suicide.