Israeli troops trying to repel rock-throwing Palestinians did not have permission to use live rounds, Israeli officials said Wednesday, but a Palestinian autopsy showed that a 10-year-old boy killed in the clash was shot by an assualt rifle.

Palestinian forensic doctors found that Ahmed Moussa was struck by a single bullet from an M16 assault rifle that entered his forehead and exited the back of his head, according to Said Abu Ali, governor of Ramallah.

The boy was killed on Tuesday in the village of Naalin, during one of the frequent protests there against Israel's West Bank separation barrier. The Israeli military said it was investigating the boy's death.

Children dying in clashes between Israel and Palestinians is a sensitive issue for both sides, making impartial autopsies crucial to determining events. Both sides frequently accuse each other of exaggerating events.

Israel sought to do a joint autopsy with the Palestinians either in Israel or in the West Bank, but Palestinian officials refused, Ali said.

The troops did not have permission to use live fire, Superintendent Sharon Manor, a company commander in Israel's Border Police, told Israel's Army Radio on Wednesday, but she did not say whether that was what killed the boy.

Residents of Naalin protest almost daily against Israel's separation barrier, which threatens to take over hundreds of acres of Naalin's olive groves. The demonstrations frequently turn into confrontations between stone-throwing youths and Israeli troops firing tear gas and rubber-coated bullets.

On Tuesday, Israeli forces started erecting a makeshift fence to prevent protesters from reaching bulldozers clearing land for the barrier. Protesters said troops fired tear gas, rubber bullets and then live fire to disperse demonstrators trying to scale the fence.

One of the bullets struck Moussa. He was buried following a mass funeral in Naalin Wednesday.

Israeli soldiers usually do not use live fire to quell the protests.

Late Wednesday, a 21-year-old Palestinian protester was critically wounded, a Ramallah Hospital doctor said, when he was hit in the head with two rubber-coated steel pellets fired by Israeli forces. The military said it was investigating.

Israel's military said its initial investigation into the shooting of Moussa indicated youths were hurling "rocks in very large quantities."

Israeli border police said they would deploy forces better trained in riot control to deal with the protests.

"This type of incident will not repeat itself," Manor said.