The UN commissioner said on Friday that "the incidents that preceded the Minister's death are disturbing and must be carefully investigated".
Zeid stressed that the investigations must be impartial and transparent.
"I note that the Israeli Defense Forces have said they have launched an investigation into the circumstances of Abu Ein's death. I welcome that, but would like to stress that this investigation – and all others involving possible excessive use of force — should be thorough, effective, independent and impartial. It must also be quick and utterly transparent if people are to have faith in its findings," the UN commissioner said.
Ziad Abu Ein, head of the Palestinian Authority committee against the separation wall and settlements, died after Palestinian protesters clashed with the Israeli military on Wednesday. According to local media, an Israeli soldier hit the official in the chest with a helmet during an olive-tree planting protest in the occupied West Bank village of Turmusiya (Turmus'aya) near Ramallah.
Palestinians want to create an independent state on the territories of the West Bank, including East Jerusalem, partially occupied by Israel, and the Hamas-controlled Gaza Strip, and want Israel to withdraw from the Palestinian territories it took after the Six-Day War in 1967.
In October, Palestinians worked out a draft UN Security Council resolution that defines strict time limits for Israel to end its occupation and remove its settlements before November 2016.
