The latest in a series of protests against the plans, which were paused last month in the face of a wave of strikes and mass demonstrations, come as Israel faces a sharp rise in tensions on several fronts during the Muslim holy month of Ramadan.

Around Al-Aqsa mosque in Jerusalem, tens of thousands of worshippers were expected for evening prayers amid concerns over a possible repeat of nighttime police raids this week that were followed by rocket barrages into Israel and Israeli strikes into Gaza and Southern Lebanon.

Israelis were also on edge after a car-ramming in Tel Aviv on Friday that killed an Italian man and wounded five other tourists, hours after a gun attack killed two Israeli sisters and wounded their mother near a settlement in the occupied West Bank.

Netanyahu has mobilised border police reservists and ordered the army to reinforce security positions to head off possible trouble, amid calls for calm from the United Nations, the European Union and the United States.

In central Tel Aviv, crowds waving the blue and white Israeli flags that have become a hallmark of the protests over the past three months gathered in a show of defiance against plans they see as an existential threat to Israeli democracy.

The demonstration began with a prayer for the victims of the attacks a day earlier but protesters said they would not be put off by security worries.

"Security is one thing but reform is another," said 26-year-old student Amitay Ginsberg. "We're still going to come here and say loud and clear that we will not let this reform pass."

The proposals, which would give the government effective control over the appointment of Supreme Court judges and allow parliament to overrule many decisions of the court, have caused one of the biggest domestic crises in Israel's recent history.

Hundreds of thousands of demonstrators, including army reservists, business leaders, members of Israel's tech industry and leading academics have taken part, facing off against supporters of Netanyahu's religious-nationalist coalition.

The government side, which accuses activist judges of increasingly usurping the role of parliament, says the overhaul is needed to restore a proper balance between the judiciary and elected politicians.

Critics say it will remove some of the vital checks and balances underpinning a democratic state and hand unchecked power to the government.

Before the protests, police had urged people to leave roads clear to allow emergency services to move freely following Friday's car-ramming on a popular shoreline promenade in Tel Aviv.