JERUSALEM — As many as 400,000 Israelis demonstrated on Saturday night against the high cost of living and for social justice in one of the largest protests in the nation’s history, although questions remained about about what it might achieve.

The mass protest across the country had been planned for weeks and was considered by many to be the grand finale of the street phase of the social dissent that has swept Israel this summer. Organizers initially billed it as a million-person march, but had tried to lower expectations over the last few days, saying that it would be considered a success if the turnout equaled the 300,000 people who took to the streets on Aug. 6.

The police estimated that more than 300,000 people turned out on Saturday night, but a company monitoring the turnout for the Israeli news media said the total was about 400,000, with almost 300,000 gathering in Tel Aviv alone. Tens of thousands more rallied in Jerusalem, Haifa and other cities.

The nationwide protest came after a lull in the movement over the last two weeks. The country’s attention was first diverted by a mid-August attack by Palestinian militants that killed eight Israelis near the southern city of Eilat, near the Egyptian border, and a subsequent flare-up in violence along the Israel-Gaza border.