Israeli police on Tuesday arrested 10 members of extremist anti-Arab group Lehava which has been linked to an attack last month on a Jewish-Arab school.
The attack, which incited violence against Arabs and equated them to a "cancer", sparked a wave of condemnation and came amid months of rising tensions and unrest in Israel and the Palestinian territories.
"Ten suspects, members of the Lehava organisation, have been arrested for questioning following incitement and calls for racist acts of violence and terror," the police said in a statement.
The suspects were arrested at their homes in the Israeli towns of Petah Tikva and Netivot, as well as in Jerusalem and Jewish settlements in the occupied West Bank.
Police also seized computers belonging to the suspects.
Among those detained was Lehava leader Bentzi Gopstein, who lives in the flashpoint West Bank city of Hebron.
Gopstein's lawyer said the arrests were political.
"The police are acting against Lehava even though it's a legal organisation fighting against assimilation," Itamar Ben Gvir said, accusing the "left" of pressuring the police into making arrests.
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Leftwing MPs have demanded that Lehava be banned as a "terrorist organisation".
Three Lehava members were arrested last week on suspicion of torching a classroom at the Hand-in-Hand school, a rare symbol of coexistence in Jerusalem.
The November 29 attack saw the classroom badly damaged and slogans including "Death to Arabs" and "There's no coexistence with cancer" scrawled on the walls in Hebrew.
Prime Minister Benjamin Netanyahu and other senior officials condemned the attack at the 624-pupil school on the Green Line separating west Jerusalem from the annexed eastern sector.
It came as tensions ran high in Jerusalem after a spate of deadly Palestinian attacks against Jews, including cars ploughing into groups of Israelis and a bloody assault on a synagogue that killed four worshippers and a policeman.
Lehava activists follow the teachings of the late Meir Kahana, a virulently anti-Arab rabbi whose Kach party was banned in Israel, and its members fight against intermarriage.
Kahana was murdered in New York in 1990, but his ideology still inspires loyalty among Jewish extremists.
One Kahana follower, Baruch Goldstein, massacred 29 Muslim worshippers at a Hebron mosque in 1994.
Gopstein has said Lehava does not act illegally, and accused the Shin Bet internal security agency of trying to frame Lehava to thwart its "holy work of saving the daughters of Israel".