A senior United Nations (UN) diplomat has condemned the killing of veteran Al Jazeera journalist Shireen Abu Akleh in the West Bank on Wednesday.

UN Special Coordinator for the Middle East Peace Process Tor Wennesland sent his deepest condolences to the reporter's family and "called for an immediate and thorough investigation, and for those responsible to be held accountable," UN Secretary-General's Deputy Spokesman Farhan Haq told reporters in New York.

Abu Akleh was one of Al Jazeera's best-known reporters. She was shot dead while covering an Israeli military raid in the occupied West Bank.