Of 251 captives seized during Hamas's October 7 attack on southern Israel that triggered the ongoing war, 97 are still held in the Gaza Strip including 33 the Israeli military says are dead.
Weekly rallies have sought to keep up pressure on the Israeli government, accused by critics of stalling on a deal to free the remaining hostages.
Protest organisers say crowd sizes have swelled this month after an announcement by Israeli authorities that six hostages whose bodies were recovered by troops had been shot dead by militants in a southern Gaza tunnel.
One of the six was Alexander Lobanov, whose wife Michal on Saturday addressed the crowd in Israel's commercial hub of Tel Aviv, asking why the government did not "do everything" to bring him back alive.
"It was possible to save them, to rescue them through a deal," she said, according to excerpts of her remarks provided by the Hostages and Missing Families Forum campaign group.
"True, it's not as heroic as a military rescue, but it's a different kind of bravery."
Thousands of people joined the rally in Tel Aviv and another in Jerusalem, seat of the Israeli parliament, AFP correspondents said.
Prime Minister Benjamin Netanyahu's government is facing rising anger from critics who accuse him of not doing enough to secure a truce deal that would see hostages exchanged for Palestinian prisoners held in Israeli jails.
The vast majority of the hostages freed so far were released during a one-week truce in November. Israeli forces have rescued alive just eight.
- 'No point anymore' -
The October 7 attack resulted in the deaths of 1,205 people, mostly civilians, according to an AFP tally based on Israeli official figures.
Israel's retaliatory military campaign to destroy Hamas has killed at least 41,182 people in Gaza, according to the Hamas-run territory's health ministry.
Talks mediated by the United States, Egypt and Qatar to reach a deal between Israel and Hamas have stalled for months.
Demonstration organiser Noa Ben Baruch, 48, told AFP in Tel Aviv that "the urgency is unparallelled. It's not only the hostages, it's everything."
As the war rages on for more than 11 months with no end in sight, "there is no point to it anymore", she said.
"This war has to end yesterday. It's futile."
Around her members of the crowd waved Israeli flags and signs that read "Bring them home", "Seal the deal", "End the bloodshed" and "They trust us to get them out of hell".
A group of women wore black t-shirts and jeans stained with fake blood, recreating a widely circulated picture of soldier Naama Levy taken when she was abducted on October 7.
In both Tel Aviv and Jerusalem, the names of hostages were read out on loudspeakers.
Tel Aviv resident Ran Eisenberg, 77, said rescuing them should be the government's top priority.
"The fact that it doesn't happen really makes me very frustrated," he said.
Hezbollah warns Israel against Lebanon border flare-up
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ADDS new Israeli strikes
Hezbollah's second-in-command warned on Saturday that an all-out war by Israel aimed at returning 100,000 displaced people to their homes in areas near the Lebanon border would displace "hundreds of thousands" more.
Naim Qassem, number two in the Iran-backed Lebanese group, was speaking after Defence Minister Yoav Gallant said Israel was determined to restore security to its northern front.
Gallant told Israeli troops last week that "we are preparing for anything that may happen in the north".
In a speech in Beirut, Qassem said: "We have no intention of going to war, as we consider that this would not be useful.
"However, if Israel does unleash a war, we will face up to it -- and there will be large losses on both sides," he said.
"If they think such a war would allow the 100,000 displaced people to return home ... we issue this warning: prepare to deal with hundreds of thousands more displaced."
Hezbollah has traded near-daily fire with Israeli forces in support of ally Hamas since the Palestinian militant group's October 7 attack on Israel triggered war in Gaza.
Thousands of people living in the border area of both countries have been displaced by the fighting.
On Saturday evening, the Israeli military said its air force had struck suspected Hezbollah weapons storage facilities at two locations in Lebanon's eastern Beqaa Valley, as well as in six locations in the south.
Three children were among four people wounded in an Israeli strike in the northern Beqaa's Hermel district, some 140 kilometres (85 miles) from the Israeli border, the Lebanese health ministry said.
A source close to Hezbollah said the strike targeted a farm in the area, a stronghold of the militant group.
A second strike on the village of Serine, near Baalbek, targeted "warehouses storing food products", the source added.
The cross-border violence since early October has killed 623 people in Lebanon, mostly fighters but also including at least 142 civilians, according to an AFP tally.
On the Israeli side, including in the annexed Golan Heights, authorities have announced the deaths of at least 24 soldiers and 26 civilians.