The closure may remain in effect until after the High Holy Days.

"Israel will not stand for the targeting of its citizens and will respond with a strong arm against all terror organizations," Prime Minister Benjamin Netanyahu told his cabinet Sunday.

The killings occurred just after U.S. Middle East envoy Dennis Ross arrived in the region last week. As of Wednesday, Ross had been unable to move the talks ahead. He was expected to leave the region by today.

One of the main sticking points is Israel's demand to renegotiate an understanding on security cooperation worked out in December by Israeli, Palestinian and U.S. officials.

The understanding calls in part for a Palestinian crackdown on Hamas. Netanyahu has rejected the initial understanding as insufficient.

Palestinian officials assert the slaying of the Awadallah brothers was aimed at scuttling the peace process.

However, Netanyahu spokesman David Bar-Illan countered that Israel pursues suspected terrorists at all times regardless of the possible repercussions.

On Thursday of last week, Israeli soldiers stormed a one-room house near Hebron and killed the Awadallahs, who were senior members of Izzadin al-Kassam, the Hamas military wing.

Troops found a weapons cache, including an Uzi submachine gun, an assault rifle, grenades, two pistols and several wigs or hairpieces, including earlocks worn by some observant Jewish men. A large banner reading "Izzadin al-Kassam" covered one wall.

Army officials said the brothers were planning to kidnap Israelis or carry out a drive-by shooting.

Also on Thursday of last week, Kamale Nader, a 41-year-old widowed mother of four, died in a hospital. The Palestinian woman was struck in the face by a rubber bullet five days earlier during riots in a northern Jerusalem refugee camp. Israeli police confirmed that she was not participating in the riots. She got caught up in the crowds when she was out buying food for her family.

The killings of the two brothers sparked several days of confrontations in the West Bank between Israeli troops and Palestinian demonstrators calling for revenge. Riots were staged in or near Ramallah, Nablus, Hebron, Bethlehem, Bir Zeit and Tekoa.

Scores of Palestinians were injured.

The worst clashes were reported in El Bireh, the Awadallahs' hometown, where thousands of protesters marched Saturday from nearby Ramallah. They threw stones and bottles at Israeli soldiers, who responded with rubber bullets.

Cries of revenge from Hamas leaders have been constant since the killings. Hamas founder Sheik Ahmed Yassin called for retaliation.

"We will not forget the blood of our martyrs," Yassin said.

Mahmoud Zahar, a top Hamas official in the Gaza Strip, said that "Israel will pay a high price for this crime." He added that Hamas would retaliate with suicide bombings similar to those carried out after its chief bombmaker, Yehiya Ayash, was assassinated in January 1996.

The deaths of the Awadallah brothers, and the subsequent threats of reprisals, have prompted some debate in Israel about the value of the operation, given the potential costs in Israeli blood.

Israeli officials countered that the operation prevented a terror attack. By killing two top Hamas militants, they added, Israel has also seriously crippled the militants' ability to plan and carry out additional attacks.

Israel asserts that Adel Awadallah, commander of the Hamas military wing in the West Bank, masterminded several suicide bombings. He topped Israel's most-wanted list.

Imad Awadallah escaped last month from a Palestinian jail. He had been held on suspicion of involvement in the March killing of the chief Hamas bombmaker, Mohiyedine Sharif. His body was found in Ramallah riddled with bullets and burned by an explosion.

Hamas blamed Israel for Sharif's death, a charge promptly denied by Israeli officials. The Palestinian Authority said that both brothers were responsible for that slaying.