A Palestinian director of the Oscar-winning documentary “No Other Land” was beaten bloody near his home by Israeli settlers and detained by the Israeli authorities in the occupied West Bank on Monday evening, witnesses said.

The director, Hamdan Ballal, was set upon in Susya, his home village, by at least 20 masked people,mostly teenagers armed with rocks, sticks and knives, according to Joseph Kaplan Weinger, 26, who said he had come upon the attack after it began. Mr. Weinger is part of a volunteer initiative that provides protection in areas vulnerable to settler violence.

It was not clear what  prompted the attack, but Mr. Weinger, who is also a doctoral student in  sociology at the University of California in Los Angeles, said the group had descended on Susya, which is south of Hebron, and assaulted West Bank residents as they were breaking the fast during the holy Muslim month of Ramadan. Some mockingly shouted holiday blessings as they did so, he said.

Mr. Weinger said that he began honking the car horn in an attempt to alert nearby Israeli soldiers to the attack, but that the Israeli forces prevented him and two companions from reaching Mr. Ballal’s home.

“Soldiers just stood around,” he said. “Later, when we got there, we saw his blood on the ground.”

Mr. Ballal, 37, was one of three Palestinians detained, according to witnesses and the Israeli military. Leah Zemel, a lawyer representing the detainees, said that she had been informed that they were being held in a military center for medical treatment ahead of questioning, but that she did not know the reason for their detention.

The Israeli military said in a statement that “several terrorists” had hurled rocks at Israeli citizens, damaging their vehicles near Susya and prompting a “violent confrontation” that involved “mutual rock hurling between Palestinians and Israelis.” The military 
said that when its forces and the police arrived, “terrorists” threw rocks at them.

Three Palestinians suspected of hurling rocks, as well as an Israeli civilian, were detained “for further questioning by the Israel police,” the statement said. An Israeli was injured and was transported to receive medical treatment, it said.

The assault on Mr. Ballal came as the Israeli military has been conducting intense raids in the West Bank, in what it says is an effort to crack down on militant groups. Since January, the operation, focused on the northern West Bank, has forced more than 40,000
Palestinians to flee their homes— the biggest displacement of civilians in the territory since the Arab-Israeli war of 1967, historians say.