Palestinian medics told the BBC Ziad Abu Ein died from complications related to exposure to tear gas during the incident near the village of Turmusaya.

But several witnesses said the minister had been hit and shoved by soldiers. One said he had been hit in the chest by a tear-gas canister fired by them.

The Israeli military said it was looking into the reports.

In recent weeks, 10 Israelis and an Ecuadorean have been killed by Palestinians in a series of attacks. Thirteen Palestinians have also been killed, among them several of the assailants.

'Barbaric act'

Mr Abu Ein, a minister without portfolio, was among dozens of foreign and Palestinian activists who took part in a protest against land confiscations.

A protester carries an olive tree sapling he had planned to plant on a patch of land near the Jewish settlement of Shilo in the West Bank (10 December 2014)

Protesters had planned to plant olive tree saplings on a patch of land they fear will be annexed by Israel

Ziad Abu Ein argues with Israeli troops at a protest in the West Bank (10 December 2014)

As they approached the land, the protesters - led by Mr Abu Ein - were stopped by Israeli soldiers

They had planned to plant olive tree saplings on a patch of land near the Jewish settlement of Shiloh, which Palestinians believe has been earmarked for annexation by Israel.

In the course of the protest, they came into confrontation with a group of about 15 Israeli soldiers.

Leading Palestinian activist Mahmoud Aloul, who was also at the protest, told the Associated Press the soldiers had fired tear gas at the activists and had beaten some of them with rifle butts.

At one point, Mr Abu Ein was hit by a tear gas canister, Mr Aloul said.

The Reuters photographer said he had seen Mr Abu Ein being struck by a hand to the neck during an altercation with two of the soldiers. An AFP news agency photographer said the minister had been hit in the chest.

Photos of the incident showed Mr Abu Ein lying unconscious before he was removed from the scene in an ambulance. He died before reaching hospital in the nearby city of Ramallah.

Palestinian medics told the BBC that the minister had died from complications related to exposure to tear gas, but the director of the Ramallah hospital told the AFP news agency that Mr Abu Ein had been "martyred after being beaten in the chest".

There are reports that Mr Abu Ein had a health condition that may have contributed to his death.

The BBC's Kevin Connolly in Jerusalem says Palestinians are likely to see the exact cause of death as a secondary issue, and it will serve to sharpen political tensions.

Condemning "the brutal assault" on Mr Abu Ein as a "barbaric act that cannot be tolerated or accepted", Palestinian Authority President Mahmoud Abbas promised to take unspecified measures and declared three days of mourning.

A senior Palestinian official said the Palestinian Authority would halt security co-ordination with Israel.

Mr Abu Ein once received the death sentence, commuted to life imprisonment, from a court in Israel for a 1979 bombing that killed two Israeli teenagers.

He was released in 1985 as part of a prisoner exchange that saw the release of three Israeli soldiers captured in Lebanon.