Israeli troops and police have clashed with Jewish settlers in the West Bank trying to prevent a settlement outpost being dismantled.
Settlers have vowed to make the army's job as difficult as possible
Hundreds of hard-line settlers converged on the Mitzpeh Yitzhar outpost near Nablus, and tried to block roads with boulders and burning tyres.
Some were reported to have been arrested, but the Israeli security forces are mostly unarmed and said they were trying to use minimal force.
The Israeli action is the first against an inhabited settler outpost in the West Bank under the latest US peace plan known as the roadmap.
It comes as US Secretary of State Colin Powell is poised to return to the region for talks with Israeli and Palestinian leaders.
Mr Powell is quoted as saying there had been some progress in talks between the Palestinian prime minister and Palestinian militant groups on ending attacks on Israelis.
There were scuffles at the Mitzpeh Yitzhar outpost - a collection of huts and tents set up last year in the heart of the West Bank - where hundreds of teenage settlers gathered, some of them chanting, singing and praying.
The BBC's James Reynolds, who was at the site, said some of the settlers placed a pile of stones in the road to block the army's way, and when soldiers removed the stones, the settlers put them straight back.
Settlers also set fire to some of the surrounding scrubland to try to prevent soldiers getting to the site.
Troops have taken down a big tent at the site, but other huts and tents are still standing.
Yosi Peli, a resident of a nearby settlement, said: "This is our land, our home. Tomorrow we will be here again on this hill or on other hills."
Israel has agreed to dismantle settlements built without government authorisation as part of its obligations under the roadmap.
The assault on the settlement outpost began just hours after a Palestinian suicide bomber killed himself and an Israeli shopkeeper in northern Israel.
A witness, Asher Ben-Moussa, told Israel Radio that the young man had walked into a grocery shop in the village of Sde Trumot, near the West Bank, before blowing himself up.
Israel has insisted that an end to violence is a vital precondition for moving ahead with the roadmap.
The push for peace will be at the top of the agenda on Friday when Mr Powell visits Israel and the Palestinians.
ROADMAP MAIN POINTS
Phase 1: End to Palestinian violence; Palestinian political reform; Israeli withdrawal and freeze on settlement expansion; Palestinian elections
Phase 2: (end of 2003) Creation of an independent Palestinian state; international conference and international monitoring of compliance with roadmap
Phase 3 (2004-2005): Second international conference; permanent status agreement and end of conflict; agreement on final borders, Jerusalem, refugees and settlements; Arab states to agree to peace deals with Israel
Last week, the Israeli authorities demolished a number of uninhabited mobile homes on settlement outposts. Settlers responded by setting up new outposts.
The BBC's David Chazan in Jerusalem says the latest action follows intense pressure from Washington on Israeli Prime Minister Ariel Sharon.
The Bush administration wants Israel to remove all the settlements that have been built in the Palestinian territories over the past two years.
But our correspondent points out that Mr Sharon is also under pressure from the settlers themselves, whose activities he once encouraged.