Updated

The United States gave Israel advance warning of its opening strike in operations against Iraq, a senior Israeli official said Thursday as Israeli civilians began carrying gas masks to protect them from a possible Iraqi retaliation.

Prime Minister Ariel Sharon received word from the Bush administration, said Maj. Gen. Amos Gilad, the official government spokesman concerning the Iraq campaign.

Also Thursday, about 700 Palestinians in the Gaza Strip -- most of them schoolchildren -- waved Iraqi flags and posters of Saddam Hussein and burned two U.S. flags in protest of the U.S.-led war.

Among the slogans shouted in the northern Gaza town of Beit Hanoun early Thursday were, "Death to America, death to Bush," and "We will sacrifice our soul and our blood for Saddam."

The military on Wednesday instructed civilians to remove gas masks from boxes and install their filters. The announcement said Israelis should carry their gas masks with them everywhere they went, and children took their masks to school on Thursday.

Several thousand Israelis in the Tel Aviv area, the target of Iraqi Scud missiles during the 1991 Gulf War, were leaving for safer parts of the country -- such as Jerusalem, unlikely to be hit because of its holy sites, or Eilat, at Israel's southern tip and out of Iraqi range.

Still, a poll showed that 84 percent of the Tel Aviv region's 2 million people did not plan to leave. The survey in the Yediot Ahronot daily questioned 505 people and had a margin of error of 4.5 percent.

Israeli experts and officials continued to reassure their people that the probability of an Iraqi attack against Israel in retaliation for a U.S.-led assault was low. Most Israelis were displaying concern but no panic.

"We don't intend to have a high profile in this war," Foreign Minister Silvan Shalom said Thursday.

During the last Gulf War against Saddam Hussein, Iraq fired 39 Scud missiles at Israel, causing damage but few casualties. The strikes were an apparent effort to provoke an Israeli counterstrike that would have undermined a broad U.S.-led coalition that included Arab nations.

This time, however, most of the Arab world opposes the war against Iraq. Iraq has not threatened Israel, insisting it has no non-conventional weapons and will not carry the war beyond Iraqi borders. U.S. officials reject the Iraqi assurances, and some Israelis were nervous.