A spiral of vandalism and arson was sparked by a Hamas gun ambush last week near a settlement that killed four Israelis. The rioters came from settlements, have numbered in the hundreds and included masked and armed men, Palestinian witnesses said.

Palestinian officials have accused Israel's military, which is widely deployed in the West Bank, of ignoring or even abetting the rampages. Of around a dozen suspected rioters detained, at least two are off-duty soldiers, the military said.

With U.S. dual-nationals among the Palestinian victims, Washington - already at loggerheads with Israel over settlement construction - has stepped up condemnation of what it had called "extremist settler violence" and said it expects accountability.

Briefing Israel's parliament, Defence Minister Yoav Gallant deplored the rampages as "a dangerous social phenomenon that we must fight". He described the perpetrators as a "tiny group" made up of fringe settlers and their supporters from inside Israel.

While he noted that suspects were in custody and said West Bank troops had been reinforced as a precaution, Gallant also said Israeli forces would be challenged to "divide their attention" between the riots and Palestinian militant threats.

"There are 500 Palestinian villages, some of them as large as towns. There are tens of thousands of people (Palestinian residents). You can't protect all of them at once," he said.

Interdiction of fellow Israelis was hard "because you're not using surveillance or the implementation of violent (military) operations against them," he added.

The sectarian violence in the West Bank has opened up cracks between Israel's religious-nationalist government and its security chiefs, who on Saturday issued a joint statement calling the settler rampages "nationalist terrorism".

That raised hackles among Prime Minister Benjamin Netanyahu's far-right allies, who have long played down the scale and impact of the settler rampages. One of them likened the security chiefs' statement to the recent mutiny by Russia's mercenary Wagner Group, but soon apologised amid public outcry.

"An apology after the fact does not eliminate the great damage caused," military chief Lieutenant-General Herzi Halevi said in a speech. "The IDF (Israel Defence Forces) operates solely for the security of civilians, hence its authority."

"Terrorism and its difficult consequences bring some people to commit acts that are legally and ethically forbidden," he said. "An IDF officer who stands by when seeing an Israeli citizen planning to throw a Molotov cocktail at a Palestinian house cannot be an officer."

Such assurances have had little sway among the Palestinians, almost a decade since the stalling of U.S.-sponsored efforts to achieve their statehood goals through negotiations with Israel. The Palestinian Foreign Ministry has described the settler rampages as "state-sponsored terrorism."