Dozens of masked settlers gathered at an intersection near the Jewish settlement of Yitzhar on Monday after three settler caravans had been removed from a site in the northern West Bank.
The international community regards all settlement activity as illegal and Israel is committed under the peace "roadmap" agreed with the Palestinians in 2003, to stopping settlements.
Witnesses said that the settlers threw rocks at any Palestinians who were forced to stop their cars by obstructions in the road.
"They attacked when the minibus stopped. The man next to the driver was seriously wounded," Zakaria Sada, an activist with the Rabbis for Human Rights organisation, said.
The vehicle was reportedly carrying 17 Palestinian workers on their way to Israel.
When another driver stopped his vehicle, the group beat him until Israeli troops arrived on the scene, Sada told the AFP news agency.
One of the wounded is in a serious condition in hospital with a fractured skull, medics said.
When they set fire to nearby fields, Palestinians tried to chase them away by throwing stones before about 20 settlers opened fire in their direction, an AFP correspondent reported.
"It took us six months to plant everything, this is our whole life," Shaher Tawil, a Palestinian farmer, said.
His fields of wheat and olive trees on the outskirts of Far-ata were burned.
|Settlers reportedly set fire to Palestinian fields on the outskirts of Nablus [EPA]
About 500,000 Jewish settlers live among nearly three million Palestinians in the West Bank and there are frequent clashes between the two groups.
Binyamin Netanyahu, the Israeli prime minister, has said that more than 20 outposts - settlements that were erected in the West Bank without Israeli government approval - will be demolished.
"Our intention is to dismantle the unlawful outposts," he told a parliamentary committee on Monday, while pledging that construction will continue in other settlements to accommodate population growth.
Gershon Messika, the president of a settlers' organisation in the northern West Bank, said that the violence was inevitable given the plans to dismantle the outposts.
"It's natural that people who face expulsion from their house do what they can to avoid being expelled," he said.
Barack Obama, the US president, called for all settlement activity to be halted when he met Netanyahu recently.