Palestinian leaders said peace negotiations were threatened Monday after Israeli security forces fatally shot three Palestinian men during an early-morning clash in the Qalandia refugee camp there.

It was one of the deadliest incidents in the West Bank since 2009, when three Palestinians were killed in Nablus after a stand-off with Israeli forces. In addition to the three dead in the incident Monday, 15 were wounded and six were in critical condition in Ramallah hospitals, according to Palestinian officials.

A senior member of the Palestinian Authority said that a gathering scheduled for Monday, as part of the U.S.-led peace negotiations, was postponed to protest the killings.