Israel's government on Sunday rejected claims raised in documents allegedly leaked from the Pentagon that leaders of its foreign intelligence service Mossad had supported nationwide protests against a proposed overhaul of Israel's judiciary.

The New York Times on Saturday published an assessment it attributed to a Central Intelligence Update from March 1 that Mossad leadership had encouraged its staff and Israeli citizens to join the mass protests. The paper said that while the leaked documents seemed authentic, it did not mean they were accurate.

The office of Prime Minister Benjamin Netanyahu said in a statement that the report was “mendacious and without any foundation whatsoever”.

"The Mossad and its senior officials did not and do not encourage agency personnel to join the demonstrations against the government, political demonstrations or any political activity,” it said.

Netanyahu's overhaul plan has sparked unprecedented public anger since his coalition of hard-right and religious parties came to power late last year, and has also caused alarm among Israel's Western allies.

The proposed legislation would enable Parliament to override the Supreme Court decisions and hold control over judicial appointments.

After weeks of intensifying demonstrations, Netanyahu in late March relented and said he would delay the contested reforms to allow for compromise talks with opposition parties.

The US justice department said on Friday it was in touch with the defence department and had begun a probe into the leak of the alleged documents, covering several subjects relating to national security. It declined further comment.