Updated

Jewish extremists angry over limits on West Bank construction have threatened to kill the defense minister, prompting the government to beef up security around him, officials said Wednesday.

They said the internal security service, or Shin Bet, was investigating the threats and that Ehud Barak's security has been reinforced in recent weeks.

Such threats are taken seriously in Israel after Prime Minister Yitzhak Rabin was assassinated in 1995 by a Jewish extremist opposed to his peace moves with the Palestinians.

The officials spoke on condition of anonymity because they were discussing a sensitive security issue.

Channel 10 TV showed a picture of a threatening letter on its evening newscast Wednesday.

Speaking in Tel Aviv later Wednesday, Barak referred to the letter. "I am not afraid of anything or anyone, and that goes for the threats as well," he said.

Prime Minister Benjamin Netanyahu announced the settlement restrictions in November, triggering an angry backlash from West Bank settlers, who fear the measure is a first step toward dismantling their West Bank communities as part of a future peace agreement.

Settlers have repeatedly tried to block inspectors from enforcing the ban, and in some cases, the protests have turned violent. Much of the anger has been directed at Barak, who leads the centrist Labor Party and who oversees construction policies in the West Bank.

While mainstream settler leaders have urged people to use nonviolent tactics, security officials are concerned about the intentions of a small number of extremists living in the West Bank.

In November, authorities arrested a U.S.-born settler and charged him in the shooting deaths of two Palestinians and trying to kill others in a string of attacks on people who disagreed with his views.

The security officials said additional bodyguards have been assigned to Barak for several weeks following numerous threats against him.

The letter shown on TV said, "Mr. Ehud Barak, if you (think) you will destroy the settlements in Judea and Samaria and be nice to the Americans, you're mistaken. I will murder you before that happens," the letter said, referring to the West Bank by its biblical name.

A spokesman for the Shin Bet said the letter is being investigated. He refused to give details on changes in Barak's security detail, saying only that "we always conduct assessments and make changes according to the situation." He was not allowed to be identified by the secretive agency.

Settler leader Dani Dayan said whoever wrote the letter is "delusional" and should be prosecuted. "We reject this threat fully," he told Army Radio.

Israeli TV commentators said the handwriting and language in the letter indicated it was written by a youth. Nonetheless, Yitzhak Paltik, the former head of the Shin Bet division that tracks Jewish extremists, said it should be taken seriously.

"No threat should be taken lightly, even if on the surface it seems to be just a child or any of the other speculation regarding the sender of the letter," he told Army Radio. Rabin was assassinated by a young university student at a time when he was receiving numerous threats from extremist groups.

Netanyahu announced his partial freeze on West Bank settlement construction in hopes of persuading the Palestinians to restart peace talks. The order bars construction of new homes in Israel's more than 120 West Bank settlements.

The Palestinians say the order is insufficient because it does not apply to 3,000 homes already under construction and does not include east Jerusalem, the disputed section of the holy city they claim as their future capital.

Also Wednesday, the Israeli military said its top commanders will consult more closely with its legal advisers during future offensives — a move motivated by war crimes accusations that followed last year's war in the Gaza Strip.

The army said the decision formalized a practice already used during the Gaza war.

The policy follows a U.N. panel's conclusion that Israel committed war crimes in connection with the Gaza operation. Both military and political officials have been forced to cancel trips to Britain because of efforts by Palestinian activists to bring them to trial under a war crimes law that breaks down jurisdictional barriers.

Israel launched the Gaza offensive to stop militants from firing rockets into southern Israel. But the operation drew widespread international criticism over the high Palestinian civilian death toll.