Commentators say the surge in attacks has been fueled by the collapse of U.S.-sponsored peace talks in 2014.

Israeli troops shot and killed two Palestinian men who tried to stab soldiers at a checkpoint in the occupied West Bank on Saturday, the Israeli military said, part of a wave of violence now in its fourth month.

The soldiers were not injured in the confrontation at Bekaot checkpoint in the northern West Bank and Israeli forces “thwarted the attack and shot the assailants,” said the military. The Palestinian Health Ministry confirmed the two men were dead.

Palestinian stabbing, car-ramming and shooting attacks have killed 21 Israelis and a U.S. citizen since Oct. 1. Israeli forces or armed civilians have killed at least 139 Palestinians, 89 of whom authorities described as assailants. Most others have been killed in clashes with security forces.

Commentators say the surge in attacks has been fueled by the collapse of U.S.-sponsored peace talks in 2014, the growth of Jewish settlements on land Palestinians want for a future state and Islamist calls for the destruction of Israel.

Also stoking the violence has been Muslim opposition to increased Israeli visits to Jerusalem’s al-Aqsa mosque complex, which is the third holiest site in Islam and is also revered in Judaism as the location of two biblical temples.

On Friday an Arab Israeli citizen wanted for a Jan. 1 gun rampage in Tel Aviv, that had left three people dead, was killed in a shootout with police after a week-long manhunt. Authorities have so far said his motives were unclear.