UPDATE 1-Israeli officer kills Palestinian assailant in W.Bank, police say

(Adds U.N., EU in paragraph 4)

RAMALLAH, West Bank, Dec 2 (Reuters) - An Israeli officer shot dead a Palestinian assailant in the occupied West Bank on Friday, border police said, an incident which the Palestinians denounced as an execution.

The man had stabbed and lightly wounded a border policeman after which another officer overpowered him. The man then fought with the officer and tried to snatch his rifle before the officer shot him dead, border police said in a statement.

The Palestinian Health Ministry confirmed his death. The Palestinian Foreign Ministry said it was tantamount to an execution meant to escalate already spiralling violence in the territory, which Palestinians seek for a state.

On Twitter, the United Nations Middle East envoy Tor Wennesland said he was horrified by the killing and the European Union said it was concerned by what appears to be excessive use of force by Israeli security forces toward Palestinians.

Border police distributed a photo of a knife on the ground and another of a border policeman with what appears to be a stabbing wound to his head.

A video circulating on social media showed an officer holding a man in a head-lock by a road as two other men try to wrestle him away. The man then appears to strike the officer and attempt to take hold of his rifle before the officer pulls out a handgun and shoots him several times as he falls to the ground.

The video, taken from a distance as vehicles cross the frame, could not be independently verified by Reuters. It does not show what had transpired prior and whether the man had been holding a knife or any other weapon before it was filmed.

A border police spokesman did not respond to Reuters requests for comment on the incident, which took place close to the city of Nablus.

The city, along with nearby Jenin, has seen intensified and often fatal Israeli military operations, since a spate of deadly Palestinian street attacks in Israeli cities in March.

The worst violence in the West Bank in years has deepened diplomatic stagnation since U.S.-brokered peace talks aimed at establishing a Palestinian state there, in Gaza and in East Jerusalem, collapsed in 2014.

The incoming Israeli government under Benjamin Netanyahu looks likely to include far-right politicians who oppose Palestinian statehood and want the Palestinian Authority (PA), which wields limited self-rule in the West Bank, dismantled.

(Reporting by Maayan Lubell in Jerusalem, Ali Sawafta in Ramallah and Nidal al-Mughrabi in Gaza; Editing by Philippa Fletcher and Daniel Wallis)