International efforts have widened to trace more than 200 schoolgirls abducted by Islamists militants in Nigeria, while France has called for African leaders to hold a summit focused on the issue.

Israel on Sunday joined the bid to find the 223 schoolgirls abducted by Boko Haram fighters in Nigeria's restive northeast four weeks ago, but Washington said U.S. troops would stay out of any rescue mission.

Israeli Prime Minister Benjamin Netanyahu on Sunday offered to help Nigeria search for hundreds of schoolgirls kidnapped by extremist Islamist group Boko Haram, his office said.

A statement said that Netanyahu, currently on an official visit to Japan, made the proposal in a telephone call to Nigerian President Goodluck Jonathan.

Below are four key questions about the wave of anti-Arab hate crime sweeping Israel.

- What are 'price tag' attacks?

Israeli Prime Minister Benjamin Netanyahu arrives in Tokyo later Sunday for a summit with his Japanese counterpart Shinzo Abe at which he is expected to raise the Iranian nuclear talks and economic cooperation.

Netanyahu is likely to press Japan to side with Israel over nuclear talks between Iran and six world powers when he meets Abe Monday afternoon, the Asahi Shimbun reported.

The head of the Roman Catholic church in the Holy Land said Sunday that Israeli hate crimes against local Muslims and Christians are souring relations ahead of a papal visit.

"The unrestrained acts of vandalism poison the atmosphere -- the atmosphere of co-existence and the atmosphere of collaboration, especially in these two weeks prior to the visit of Pope Francis," Latin Patriarch Fuad Twal said.

Israel's army on Sunday declared part of the Israeli-occupied Golan Heights a closed military zone, fearing battles on the Syrian side would spill over the ceasefire line.

An army spokeswoman told AFP the area around the Quneitra crossing was closed "for security reasons."

An Israeli ministerial committee gave its backing on Sunday to changes in the law that could block amnesty for Palestinians imprisoned for murdering Israelis.

Under the proposal passed by the committee for legislation, the courts would be empowered to prevent Israel's president from granting clemency or shortening the jail term of anyone imprisoned for murder.

Israeli Intelligence Minister Yuval Steinitz on Saturday angrily denied the latest media charge of Israeli spying on its U.S. ally and said that someone was trying to sour bilateral relations.

"One gets the impression that someone is trying to sabotage the excellent intelligence cooperation between the United States and Israel," state-owned Channel One TV and army radio quoted him as saying.

The Hamas newspaper Falastin returned to West Bank newstands Saturday after a seven-year absence as part of reconciliation between the Islamist group and its rivals in the Palestinian Authority.

An executive of Ramallah-based Al-Ayyam daily said his company's presses printed the paper overnight.

U.S. Defense Secretary Chuck Hagel will fly to Saudi Arabia, Jordan and Israel next week for talks that are expected to focus on Iran's nuclear program and Syria's civil war, officials said Friday.

"This trip will be the secretary's third to the Middle East in just over a year, and it will advance America's regional strategy in that region," Pentagon press secretary Rear Admiral John Kirby told a news conference.