Dozens of masked settlers have attacked Palestinians and set fire to cars and olive trees during the annual olive harvest in the occupied West Bank.

A BBC team witnessed one of several attacks in farmland near the Palestinian village of Abu Falah. A local official said the attacks had injured 12 Palestinians, including four dual Palestinian American citizens. A foreign journalist was also among those hurt.

Driving into the area early in the morning, we came across the first signs of the violence a stream of cars carrying wounded Palestinian olive farmers racing out along the narrow stony track, piled high with olive picking equipment, as smoke rose from several fires nearby. The bloodied face of Majdi Fheed peered out from the backseat of one car.

"We were getting our olive trees and almost 15 Jewish guys … started attacking us with guns, with rocks, with special weapons. They hit me on my head [and] my neck – look, I am bleeding!" Yaser AlKam, a council member from the neighbouring village of Turmus Aya told me Majdi - an American citizen - was attacked by settlers with nail-studded sticks, and needed treatment for deep wounds on his head. His elderly mother was also injured.

Another man ferrying the injured to hospital told us that settlers had attacked them with sticks while they harvested their olives, and had burned three cars – including one of his own.

"As soon as we got to the land and put our things on the ground, they started to come, so we ran away" said a woman next to him. Asked about the violence, a US State Department spokesperson said they were aware of the reports.

"We condemn criminal violence by any party in the West Bank and call for investigations, arrests, and convictions, of those responsible," the spokesperson said.

Watching the vehicles stream past her, 73-year-old Imm Khaldoun told me emphatically that, no matter what happened, she would always return to her land. "This is my land. It's my right [to be here]" she told me.

The UN says the past two weeks have already seen more attacks by violent Israeli settlers than during the entire harvest season last year.

Olive picking in the West Bank is now a test of speed, with trees rapidly stripped of fruit as soon as the sun rises, before violent Israeli settlers attack.

In another olive orchard nearby, we watched as dozens of farmers used power-tools to strip the trees as fast as they could – one eye on the ridge above us, where a group of settlers at a new illegal outpost had already gathered, and were watching the olive harvest below.

Standing on ladders, the Palestinian farmers worked quickly, sending streams of olives onto the plastic sheets laid out under the trees. Three villages had come together to harvest these olives, the landowner Amin Khalil, told me, as a form of protection against attack. He said his land was now surrounded by seven Jewish settlements and outposts.

All Israeli settlements are illegal under international law. Outposts – small encampments on hilltops – are illegal under Israeli law as well, but many still receive state support.

"This is a hotspot – there are seven settlements around here," Amin Khalil told me. "This year, all the people came together because when there are just a few people working alone at the edge of the village, the settlers attack. So all the families are working together today." But the tactic doesn't work today. As we watch, dozens of settlers, all dressed in black, begin moving down the hill towards us, setting fire to several groups of olive trees.

There are shouts of panic from the Palestinian farmers, yelling for children to get out of the field. Some begin swiftly wrapping up the olives to leave.

But with large numbers of people on both sides, the confrontation stalls into an uneasy stalemate. We see settlers with slingshots hurl stones towards us, and young Palestinian men running to throw stones in return.

As Israeli forces arrive, the standoff explodes into action. Settlers begin running down towards us as the farmers swiftly retreat. Some Palestinians set off fireworks to try and push the settlers back.

American journalist Heidi Levine of the Washington Post was injured in the attack. She described how dozens of settlers ambushed her as she was reporting at the scene.

"I got jumped," she said. "I was on the ground and they were kicking me and I was trying to hold onto my camera and my bag. I had my helmet and flak jacket on which protected me. They made me stand up and they kicked me again, and this went on for at least 10 minutes." In a statement, Washington Post executive editor Matt Murray said Levine had been clearly identifiable as a journalist.

"We are outraged by this unwarranted attack on a journalist doing her job and urge a thorough investigation and follow-through from authorities," he said.

The Israel Defense Forces (IDF) said personnel had been despatched to the area "following a report of a violent confrontation". It said a female journalist had been injured during the confrontation. And that "all circumstances" surrounding the incident would be examined.

As the farmers retreated, the sound of live ammunition cracked across the fields. It was unclear if settlers or Israeli forces were firing.

Minutes later, Israeli forces began firing tear gas into the Palestinian fields to end the confrontation – a well-worn Israeli pattern of managing these conflicts.

The UN says settler attacks on the olive harvest this year have so far killed one Palestinian and injured more than 120 others across the West Bank.

Illegal Jewish outposts have mushroomed here over the past few years, clustering in closer around Palestinian olive groves.

What we witnessed was part of a pattern being repeated day after day, as settler outposts here increase.

The yearly olive harvest has become a litmus test of how the policies of Israel's fiercely pro-settlement government are affecting Palestinians here, by presiding over growing violence by extremist settlers, and fuelling Jewish claims to the land.