Rally organizers said some 40,000 to 50,000 women and children would at 10 a.m. (0800 GMT) form a peaceful “human chain” along the fortified frontier and call for an end to Gaza’s isolation, intensified after Islamist Hamas took charge in June. Hamas blew open Gaza’s southern border wall with Egypt last month, allowing hundreds of thousands of needy Palestinians to cross and buy supplies.

Israel voiced fear the influx included Islamist militants intent on carrying out attacks in the Jewish state, and Egyptian security forces rounded up hundreds of suspects.

Israeli troops garrisoned along the closely monitored, fenced frontier with the Gaza Strip were on high alert and paramilitary riot police on standby, and Israeli officials urged Hamas to keep the rally in check.

“I hope that, ultimately, they understand that we are deployed and ready, that this will not be a repeat of what happened in the Philadelphi Corridor (Egypt border) a few weeks back,” Deputy Defense Minister Matan Vilnai told Israel Radio.

“We don’t plan to fool around in this regard,” he said. “We will use measures in the way we deem necessary to prevent people breaking into the state of Israel’s territory.”

Asked if this could include Israeli forces resorting to live fire, Vinai said: “Anything that must be done, will be done.”

Hamas and an allied group organizing the rally said it did not intend to storm the border with Israel, which tightened the blockade last month, limiting supplies of fuel and other goods in what it called a response to cross-border rocket fire.

“People will not break across the border, but they will show the world that the siege must be broken,” said Jamal al-Khudary, chairman of the Popular Anti-Siege Committee.

“We will try to prevent violations during the rally,” he said, adding that protesters were under instructions to stay 1 kilometer (1/2 mile) from the border and would be monitored by Palestinian police. Israeli media reported that military reinforcements on the Gaza border included artillery cannon armed with smoke shells that could be fired to disperse crowds.

Israeli Prime Minister Ehud Olmert told reporters at the start of an official visit to Japan that “Israel always takes into account different scenarios, even if they are of low probability.” Hamas, which routed forces loyal to Palestinian President Mahmoud Abbas in Gaza last June, is shunned by Israel and the West for refusing to give up its stated goal of seeing the Jewish state eliminated.

Hamas has, however, offered Israel a long-term ceasefire. (Reuters)