Israeli security forces have gone on alert ahead of the Jewish New Year's celebrations, which begin Monday evening. The alert coincides with a separate warning to Israeli tourists not to travel to resorts in Egypt's Sinai Peninsula.
Israeli police say a general security alert will remain in effect throughout the month of October, as Israelis mark major Jewish holidays.
Police officials say the alert is focused on areas surrounding Jerusalem, but the military has closed off the entire West Bank and Gaza strip, as well - something it does routinely during the Jewish high holidays to prevent attacks by Palestinian militants.
Meanwhile, anti-terrorism officials have issued an unusually stern warning to Israelis not to visit the resorts in Egypt's Sinai Peninsula, saying they have specific information that extremist groups plan to kidnap Israelis who travel there.
Foreign ministry spokesman Mark Regev says the threat of terrorist incidents in the Sinai has increased since Israel's unilateral withdrawal from Gaza.
"Unfortunately because of the more porous frontier between Palestinian Gaza and the Egyptian Sinai we are most concerned about groups inside Gaza," said Mr. Regev. "Groups like Hamas, groups like Islamic Jihad that of course cannot enter Israel because of the nature of the frontier between Gaza and Israel, but now they will in fact go through the porous crossing between Gaza and Sinai, and they will hit Israelis in Sinai."
More than 30 people were killed in Egypt, last year, during the Jewish holiday season, in a series of bombings at a luxury hotel in the Sinai resort, Taba, and at a nearby beach camp. In July, at least 64 people were killed in a terrorist attack in the Sinai resort, Sharm el-Sheik.
Egyptian authorities have arrested hundreds of individuals allegedly connected to both attacks and Israeli officials say Egyptian security forces are acting on the latest threats. An estimated 30,000 Israelis were expected to visit the Sinai, this year, during the holiday season.