Israel hopes the resignation on Friday of Egyptian President Hosni Mubarak will bring no change to its peaceful relations with Cairo, a senior Israeli official said.
"It's too early to foresee how (the resignation) will affect things," the official said. "We hope that the change to democracy in Egypt will happen without violence and that the peace accord will remain."
"We have a tough period ahead of us," Zvi Mazel, a former Israeli ambassador in Egypt, told Israel TV. "Iran and Turkey will consolidate positions against us. Forget about the former Egypt. Now it's a completely new reality, and it won't be easy."
Unlike in Israel, the rest of the Arab world, including in the Hamas-ruled Gaza strip celebrated Mubarak's resignation.
In Israel, there were reports of fireworks going off in Arab villages throughout the northern part of the country.
Palestinians in Gaza let off fireworks and shot into the air to celebrate the resignation of Mubarak, and the Islamist group Hamas called on Egypt's new rulers to change his policies.
"The resignation of Egyptian President Hosni Mubarak is the beginning of the victory of the Egyptian revolution," said Hamas spokesman Sami Abu Zuhri.
"Such a victory was the result of the sacrifices and the steadfastness of the Egyptian people," he told Reuters.
Gaza residents heard gunfire erupt across the city when news of Mubarak's departure spread, and fireworks lit up the sky.
The tiny coastal enclave of Gaza shares a border with Israel and Egypt. Both countries have imposed strict limitations on the movement of people and goods since Hamas took control of the territory, hampering Gaza's economy.
"We call upon the new Egyptian leadership to take an immediate decision to lift the blockade of Gaza and open Rafah (border) crossing permanently to allow people's free movement and in order for the reconstruction process of Gaza to begin," said Abu Zuhri.
Egypt in 1979 became the first Arab country to sign a peace treaty with Israel and has backed U.S.-led efforts to end the Israeli-Palestinian conflict.
Last week, Prime Minister Benjamin Netanyahu warned of an Iranian-style Islamist revolution in Egypt should Mubarak's Muslim Brotherhood rivals eventually take over.