NEVE DEKALIM, Gaza Strip (AP) – Thousands of Palestinians were singing and celebrating the Israeli withdrawal from Gaza when a hush swept through the crowd. “The army is coming out,” people shouted.

As all eyes turned to the left of the podium, thousands of masked Hamas gunmen marched out in formation from behind the stage to parade the Islamic militant group’s might before adoring supporters. “God is great!” the crowd chanted.

Minutes earlier, militant leaders had lined up on the podium to a warm ovation. The audience, wearing Islamic green hats and waving green Hamas flags, raised their fingers to the sky, chanted a traditional oath and renewed its allegiance to the group that many Palestinians credit with forcing the Israeli withdrawal from the impoverished Mediterranean strip.

“Everyone knows how strong they are,” said Yasser Abu Sabha, standing on his plastic chair to watch the trickling army of masked gunmen. “They worked hard and resisted. This (withdrawal) is the fruit of their work.”

The show of force, in which gunmen fired into the air, burned a cardboard model of a Jewish settlement and trampled an Israeli flag, was Hamas’ largest military-style victory parade since Israel completed its withdrawal Monday.

The rally, along with the Palestinian Authority’s persistent failure to stop people from crossing Gaza’s border, underscored Palestinian leader Mahmoud Abbas’ trouble in asserting control. Abbas pledged Friday to seal the chaotic border within “two or three days,” but previous deadlines have passed without change.

With elections approaching in January, Hamas and Abbas’ Fatah faction are locked in an increasingly bitter power struggle. Each is trying to use the pullout for political gain.

Abbas is under heavy international pressure to disarm militants, a call reiterated by Israeli Prime Minister Ariel Sharon in a speech Thursday to the United Nations.

Hamas rejects Abbas’ pleas to disarm, saying its attacks drove Israel from Gaza and that armed resistance will continue. One Hamas commander, Fathi Hamad, said that Hamas actually will build up its arms. “We will increase our production capacity and the purchase of weapons,” he said.

Fatah and Hamas have held competing victory celebrations since Israel completed its pullout Monday, and Hamas has had far bigger turnouts. Some 10,000 people joined Friday’s rally in the ruins of Neve Dekalim, which weeks ago was Gaza’s largest Jewish settlement.

Ismail Haniyeh, a Hamas leader, mocked Sharon’s latest call for Abbas to crack down.

“We tell Sharon: “Fool, you are asking the Palestinian Authority to do something you have failed to do with all your might,”‘ he said at the rally.

A delegation from Egypt’s doctors’ union, a group linked with the banned Muslim Brotherhood, joined the celebration, as did Magdy Hussein, a leader of another banned Islamic group, the Egyptian Labor Party.

Earlier Friday, hundreds of masked Hamas gunmen in military-style fatigues paraded through the abandoned settlement of Netzarim.

Ziad Abu Amr, a Palestinian lawmaker in Gaza who frequently mediates between Hamas and Fatah, said he believes the Hamas threat is exaggerated. He said the militant rallies are celebrations and not meant to defy Abbas.

But Shaker Shabat, a professor at the Al Quds Open University in Gaza, said Hamas is sending two clear messages. “The first one addressed to the Palestinian people is that Hamas is the largest military power in Gaza and it played the biggest role in kicking the occupation out,” he said. “The second is to Abu Mazen that you have to think twice before trying to disarm Hamas.”

Abbas, widely known as Abu Mazen, traveled Friday to the southern town of Rafah and promised after talks with senior Egyptian officials there to seal the border within two or three days. The Palestinians acknowledge that hundreds of assault rifles have flooded Gaza in recent days, confirming Israeli fears about giving up border control.

Abbas was joined by top security commanders and, in an unusual move, by leaders of the militant group Al Aqsa Martyrs’ Brigades. Abbas in the past has said he wants to disarm the group and fold its members into the Palestinian police. But Friday’s meeting signaled that he may deal with the group, which is responsible for dozens of attacks against Israelis, as a separate entity.

“Everybody wants to work and stand shoulder to shoulder for the sake of ending the image of chaos,” Abbas said, when asked about the presence of Al Aqsa gunmen.

Palestinian officials said early Friday that the border was quieting down. But late in the day, thousands of people overwhelmed Palestinian and Egyptian forces and crossed the border again.

Still, Egyptian and Palestinian police succeeded in limiting Gazans to crossing at only two points along the border Friday instead of at the multiple ruptures in the fence they had been using. Egyptian police laid down new barbed wire and blocked some openings with large stones.

Under an agreement with Israel, Egypt has started deploying 750 troops to secure its side of the frontier and prevent weapons smuggling.

Israeli Vice Premier Ehud Olmert said he expects Egypt to secure the border in the “coming days.”

“If not, we will have to act,” he told Israel TV. He did not elaborate.