Israeli forces sealed the Gaza Strip Sunday night and soldiers fanned out across Jewish settlements in the first scripted steps of a military evacuation that thousands of settlers in tent cities and abandoned homes here have vowed to defy. By Monday morning, they had encountered resistance by defiant settlers in several settlements.

In a brief midnight ceremony at the Kissufim crossing in southern Gaza, Israeli army officials declared Gaza's 21 Jewish settlements a closed military zone hours after infantry soldiers began taking up positions in empty blocks of tile-roofed houses. Israeli armor deployed along settlement perimeters, kicking up clouds of dust as they went.

"At this moment begins the operations," said Brig. Gen. Guy Tzur of the Israeli army's southern command, moments after a steel gate swung down over the crossing. A sign affixed to the gate read: "Stop: Entry into the Gaza Strip and presence there is forbidden by law."

The declaration began a process military officials hope will conclude Sept. 4 with the removal of the last of Gaza's 8,500 Jewish settlers, a number that has been dwindling in recent weeks. Israeli soldiers, most of them unarmed, began entering settlements Monday morning to begin knocking on doors, giving the remaining residents 48 hours to leave voluntarily or face eviction by force. Tzur predicted that more than half the residents would leave within that window, saying, "We will assist the residents to pack and we will facilitate their exit from the Gaza Strip."

Here in Gaza's largest settlement bloc, the day was marked by fasting, graveside farewells, clandestine moving preparations and twilight synagogue services on the most solemn day of the Jewish calendar, Tisha B'av. The rituals commemorating the destruction of the first and second Jewish Temples were infused with special pathos this year, although few would admit it was probably the last time the day would be marked in Gaza.

"We came here today to pray to God, to beseech Him, to beg Him," Rabbi Yossef Elnekave told a crowd of more than 1,000 people who gathered in the sandy graveyard. "We stand here trembling in fear before the creator of the world and we ask Him to protect the dead and the living in Gush Katif."

The cemetery holds only a few dozen graves. Each will be painstakingly excavated, moved and reconsecrated. It is the first time Israel has abandoned settlement blocks since its 1982 withdrawal from the Sinai Peninsula following the Camp David peace accords with Egypt.

Although opinion polls show that most Israelis favor the disengagement plan, roughly a third of the country opposes the unilateral evacuation for security reasons and out of religious beliefs that no part of the biblical land of Israel should be relinquished. But the cost in lives and money to protect 8,500 Jewish settlers living among the strip's 1.3 million Palestinians has been high, especially since the start of the far more deadly second Palestinian uprising in September 2000.

The plan's opponents say the withdrawal from Gaza, without any Palestinian concessions in return, will encourage more attacks on Israel. A memorial to the 75 Israeli civilians and the 193 soldiers who have died in Gaza since 1967 will be built in Nitzanim, the coastal community where many Gaza settlers will relocate.

In the second phase of the disengagement, once the Gaza withdrawal is complete, the military will evacuate roughly 700 settlers from four small settlements in the northern West Bank. It is expected to take several more weeks for the Israeli military to demolish the estimated 2,800 homes in Gaza and the West Bank settlements, and dismantle the network of military bases in the strip that has been protecting the communities for decades.

In recent weeks, resistance in the Gaza settlements has been shrinking to a hard-core group as many residents have left on their own. The three settlements in northern Gaza, inhabited by a mix of religious and secular residents who arrived for economic incentives, are largely empty. Military officials predict that they will encounter serious resistance in only a handful of communities, mostly in the south.

By Monday morning, resistance from defiant residents blocking entrances to five settlements prevented buses carrying journalists from entering. Army commanders were considering not serving eviction notices in those communities.

"This is my house and we are being forced to give it away to people who hate us," said Benny Attias, 51, an art teacher who moved out of his two-story house in Neve Dekalim Sunday evening after 17 years. "They think they have won and chased us out of here. For them, this is a victory for Islam over Judaism."

Throughout the day, Israeli police and soldiers established checkpoints across the rural region bordering the strip, hoping to prevent more protesters from sneaking into the settlements. Military officials said as many as 4,000 may have done so.

An estimated 7,500 members of the Palestinian security forces have been deployed on the other side of the settlement's fences in a show of force meant to discourage attacks. Prime Minister Ariel Sharon has promised a harsh response if the evacuation comes under fire, and Palestinian Authority President Mahmoud Abbas recently urged Gazans to refrain from attacks.

There were exchanges of fire early Monday between soldiers and Palestinians near the Kfar Darom settlement, and mortar shells fell in two settlements and near an army base, according to the Associated Press.

Suspected Palestinian mortar fire was also reported near the Neve Dekalim settlement early Monday. No Casualties were reported.

There were signs of settlers packing up throughout the southern settlement block on Sunday. A truck bearing the name "Boris Movers," written in Hebrew and Russian, parked at the corner of the Kissufim crossing. Shipping containers could be seen along several streets. Other families quietly packed up belongings out of sight of neighbors.

At twilight, the Ulis family, one of the block's earliest settlers, gathered at the cemetery around a small grave. The tomb held the remains of Itai Ulis, who in 1993 died of cancer at the age of 14. In hushed prayers, several dozen relatives who had traveled from across Israel to attend the service asked God for the evacuation to be called off.

Special correspondent Ian Deitch in Neve Dekalim contributed to this report.

As the sun sets, a woman prays on the beach at Shirat Hayam, one of 21 Jewish settlements in the Gaza Strip that have been declared a closed military zone. A settler visits a grave at a cemetery in the Gush Katif settlements. Jewish graves in Gaza will be carefully excavated, moved and reconsecrated over the coming weeks. Officials predict few communities will resist evacuation. A boy weeps at a cemetery during a ceremony on Tisha B'av, a day that commemorates the destruction of the first and second Jewish Temples.The home of Yakov Mazaltarin burns as his family prepares to leave the settlement of Rafiah Yam. Mazaltarin said he set fire to his buildings and knocked down walls to prevent the property from ending up in the hands of Palestinians. After closing the Gaza Strip Sunday, the Israeli army planned to give remaining settlers 48 hours to move out voluntarily or face eviction.