Militant Jewish settlers have disrupted traffic on Israel's main highway and clashed with troops in Gaza to protest against the government's pull-out plan.
The authorities fear settlers could resort to violence
Spikes and oil were thrown on the Tel Aviv-Jerusalem road, damaging about 20 cars and endangering motorists.
Later settlers and Palestinians threw stones in Gaza and troops opened fire in the air to separate the two sides.
Prime Minister Ariel Sharon said he will use an "iron fist on hooligans" who violently resist the Gaza pull-out.
Police said it was a miracle there had not been a major accident on Route One where protesters scattered nails and oil during the morning rush hour.
Thousands of officers have been deployed to prevent disruption planned by one militant settler group during the evening.
Scuffles and shots
Ultra-nationalist youths have been trying to dig themselves in at an abandoned hotel and houses in the main settlement bloc in the southern Gaza Strip.
The army moved in to evict youths from two abandoned buildings and arrested eight Jewish youths for throwing stones at Palestinians, reports said.
The youths exchanged punches and kicks with soldiers, who dragged several of them away through the dust to an army vehicle.
Other settlers have occupied an abandoned Palestinian building, from where they pelted security forces with stones and food.
On Sunday the army bulldozed about 12 buildings to prevent them from being used by settlers, but two remaining structures were soon occupied by activists.
In a separate development, Associated Press reports that an Israeli farmer began dismantling his greenhouses in Gadid settlement, describing him as the first member of the powerful agricultural sector to begin preparing for this summer's withdrawal.
Settlers who leave willingly are scheduled to receive a large compensation package and to be given new homes north of Gaza.
The pullout, which is due to begin on 15 August, will see the removal of settlers from all 21 Gaza settlements, and four of 120 in the West Bank.
Israel - which has occupied and settled the territories in defiance of international law since 1967 - will keep control of Gaza's land and sea borders and its airspace.
Settler groups strongly oppose the plan and the authorities fear the resistance could turn increasingly violent. Mainstream settler groups say they will only use passive resistance.