Police did not identify the suspects, who were taken into custody for questioning, or disclose any accusations against them. The investigation was ongoing, police said on Monday.
Prosecutions of Israeli settlers are rare.
Israeli radio station Galatz reported the suspects were Israelis and that the Shin Bet domestic security service was taking part in the investigation.
Masked Israeli settlers were filmed on Friday assaulting Washington Post photojournalist Heidi Levine, a US citizen, who was covering a Palestinian olive harvest in the West Bank.
On Saturday, European diplomats and a French mayor were attacked by masked settlers in another part of the West Bank.
The diplomats' visit coincided with US President Donald Trump endorsing Prime Minister Benjamin Netanyahu for Israel's parliamentary election on October 27.
United Nations bodies and most countries deem the settlements illegal under international law but Israel rejects this, viewing the territory as disputed rather than occupied.
The weekend violence has drawn condemnation from the United States, Israel's closest ally, and from France, Belgium and Poland, whose diplomats were attacked on Saturday.
While Foreign Minister Gideon Saar and the Israeli military blamed "Israeli rioters" for the attack on the diplomats, Netanyahu, whose coalition is projected to lose its governing majority at the election, has been more circumspect.
He has said the diplomats entered a "sensitive area with a history of confrontations without prior co-ordination" with the Israeli military, and that the facts of the attack on Levine were "unclear".
Settler attacks on the Palestinians are surging, with at least 170 since September 27, according to Yesh Din, an Israeli human rights group.
Journalists, Israeli activists and foreign observers have also been targeted.
The West Bank is home to about 500,000 settlers and at least 3 million Palestinians.
On Sunday, Reuters saw a group of at least 10 settlers, masked and dressed in black, hurling rocks at Palestinians and activists harvesting olives near the Palestinian West Bank town of Salfit, prompting the farmers to flee.
Israeli border police were in the area and shot tear gas towards the hills.
