JERUSALEM — Israel has expressed concern of a Hizbullah-sponsored attack during the Arab-Israeli summit in Egypt.

Officials said Hizbullah has ordered a major attack against Israeli civilian targets over the next day. They said the attack, most likely a suicide bombing, has been timed to the Israeli-Palestinian meeting in Sharm e-Sheik on Tuesday.

Hizbullah could also target Palestinian Authority Chairman Mahmoud Abbas, scheduled to meet Israeli Prime Minister Ariel Sharon in the Sinai resort during a gathering hosted by Egyptian President Hosni Mubarak and which would include Jordan's King Abdullah. Officials did not say how Abbas, accompanied by a huge security detail, could be attacked.

On Tuesday, Israeli authorities placed police and security forces on alert for an imminent suicide attack. Officials said the alert was at the highest level short of war and involved the establishment of police roadblocks throughout the center and south of the country. Thousands of police and volunteers have also been patroling major cities as well as the 1967 border with the West Bank.

Over the last two days, Israeli authorities have foiled several suicide attacks. In one case, a Palestinian woman preparing to leave the northern West Bank city of Jenin on a suicide mission was arrested. Officials said the planned attack was sponsored by the ruling Fatah movement, many of whose operatives have been financed by Hizbullah.

In another case, a Hamas operative was arrested near Israel's Ben Gurion International Airport. The operative was also said to have been planning a major strike.

On the eve of the Sharm summit, Palestinian gunners fired mortars toward Israeli communities in the Gaza Strip. Nobody was injured.

"Palestinian terrorism continues," Israeli Defense Minister Shaul Mofaz said. "Mortar shell and Kassam rocket attacks have decreased dramatically, but other terror activities, such as arms-smuggling, tunnel-building and more, continue just the same."

The Sharon government has been under U.S. pressure to ensure the success of the Sharm summit. On Monday, U.S. Secretary of State Condoleezza Rice urged Israel to free Palestinian prisoners and take other measures to bolster Abbas.

So far, the Israeli military agreed to reopen the leading terminal that handles cargo to and from the Gaza Strip. The Karni terminal has been closed since a Palestinian attack on Jan. 13 in which six Israelis were killed.

Israel has also agreed to the deployment of at least 750 Egyptian police commandos along the Sinai border with the Gaza Strip. The commandos would be equipped with armored personnel carriers.