JERUSALEM (AP) - AN AMERICAN demonstrator was critically wounded Friday in a clash between protesters and Israeli troops over Israel's West Bank separation barrier.

Peace activists with the International Solidarity Movement said Tristan Anderson, of the Oakland, Calif., area, was struck in the head with a tear gas canister fired by Israeli troops. The military and the Tel Aviv hospital where Anderson was taken had no details on how he was hurt.

'He's in critical condition, anesthetized and on a ventilator and undergoing imaging tests,' said Orly Levi, a spokeswoman at the Tel Hashomer hospital.

She described Anderson's condition as 'life-threatening.'

The protest took place in the West Bank town of Naalin, where Palestinians and international backers frequently gather to demonstrate against the barrier.

About 400 protesters turned out in Naalin on Friday, the military said.

Some of them hurled rocks at troops, who used riot gear to quell the unrest, it added, without elaborating.

Ulrika Jenson, an International Solidarity Movement activist, said troops fired tear gas canisters into the crowd from a hill above.

'Tristan was hit and fell to the ground,' Jenson was quoted as saying in an ISM statement.

'He had a large hole in the front of his head, and his brain was visible.' -- AP