Israeli troops will enter Jewish settlements in the Gaza Strip within hours the head of Israel's military in Gaza, Brig Gen Dan Harel, has said.
At Neve Dekalim, settlers fought with soldiers
Busloads of soldiers have been seen heading into Gaza as the 2100 GMT deadline for residents to leave looms.
The army says more than half of the settlers have gone, but there has been fierce resistance in some outposts.
Earlier, there were clashes at the largest settlement Neve Dekalim as troops moved in to take up positions.
Several people were arrested in the scuffles during which bins were set alight and the security forces had to use water cannon to break through the crowds.
"The evacuation of Neve Dekalim will start in a few hours," Gen Harel said.
"In the next few hours we will go to the houses of the settlers in Neve Dekalim and we will demand that they go. It's the start of the forced evacuation but we will not use violence."
On the Palestinian side, marchers have been celebrating the pullout.
Thousands of settlers have ignored the eviction notices delivered by security forces on Monday and they have been joined by Jewish hardliners from Israel and the West Bank.
The BBC's Orla Guerin in Neve Dekalim says the latest protests have been ugly and full of anger.
Settlers, many of them women and children, struggled hand to hand with their own troops.
Insults were hurled at the unarmed soldiers and Jews could be heard calling fellow Jews "Nazis", our correspondent says.
Defence Minister Shaul Mofaz has made it clear that the troops will enforce the eviction orders.
"We will make every effort... to have law and order in this process and anyone who acts illegally will be treated according to the law," said Mr Mofaz - who added that the evacuation would take about a month to complete.
The army says the more aggressive part of its disengagement plan will begin once the deadline has passed - starting by removing the thousands of Israelis who have joined the protesting settlers.
This is the first time Israel has decided to dismantle settlements built on Palestinian land seized in 1967.
In a TV address on Monday, Prime Minister Ariel Sharon said Israel could not "hold on to Gaza forever" and that withdrawing was the best way to ensure security.
Palestinian leader Mahmoud Abbas has hailed the withdrawal as "historic" but said Israel should also pull out of the West Bank.
In the Palestinian town of Khan Yunis, the militant group Hamas is holding a demonstration to celebrate the pullout - which it views as a victory.
Hamas has promised not to attack settlers and troops as they leave the Gaza Strip.