Trucks carrying humanitarian aid entered the Gaza Strip on Sunday after a long-awaited truce between Israel and Hamas came into effect, the United Nations said.

"First trucks of supplies started entering" minutes after the ceasefire took effect on Sunday morning, UN aid official Jonathan Whittall, interim chief of the UN's OCHA aid agency for the Palestinian territories, said on X.

"A massive effort has been underway over the past days from humanitarian partners to load and prepare to distribute a surge of aid across all of Gaza."

Israel released 90 Palestinian prisoners on Monday after Hamas handed over three Israeli hostages, completing the first exchange under a long-awaited truce aimed at ending more than 15 months of war in Gaza.

The three hostages released Sunday, all women, were reunited with their families and taken to hospital in central Israel where a doctor said they were in stable condition.

People gathered in Paris Saturday in support of the hostages held in Gaza, describing being torn between hope and fear hours before a truce set to allow their release takes effect.

The ceasefire, intended to pave the way to an end of the Israel-Hamas war, was scheduled to begin at 0630 GMT Sunday.

Under the deal, 33 hostages taken by militants during Hamas's October 7, 2023 attack on Israel will be returned from Gaza during an initial 42-day period.

In Paris, hostage supporters gathered opposite the Eiffel Tower anxiously awaiting the ceasefire.

Israelis gathered in Tel Aviv to demand freedom for hostages held in Gaza, anxious the ceasefire deal would collapse, with many dwelling on the fate of Kfir Bibas, the youngest captive whose second birthday fell on Saturday.

"Today, I tried to write a birthday message for Kfir for the second time," his aunt Ofri Bibas Levy said. "A message for a child who cannot celebrate... A child trapped in hell. A child who might not even be alive. But no words come out, only tears."

Thousands of people gathered and over 70 were arrested at a pro-Palestinian rally in central London Saturday, on the eve of the start of a ceasefire between Israel and Hamas.

The majority were detained on suspicion of breaching the authorised perimeter for the protest near key government buildings in central London.

United Nations chief Antonio Guterres said Saturday a "more hopeful" future awaits Lebanon after meeting its new leaders in a two-day visit ahead of a deadline for implementing a fragile Israel-Hezbollah ceasefire.

His visit comes amid fresh optimism for crisis-hit Lebanon after a devastating war, as Joseph Aoun was elected president on January 9 and named Nawaf Salam as prime minister-designate following a two-year vacuum.

Israeli police said that an assailant stabbed and seriously wounded a person in the centre of commercial hub Tel Aviv on Saturday, before being shot and "neutralised" by a civilian.

The attack came hours before a ceasefire is set to take effect in the Gaza Strip, where Israel has been fighting Palestinian militant group Hamas for more than 15 months.

The police had initially spoken of a shooting with several wounded but clarified in a later statement that the "terrorist" was armed only with a knife.

When Donald Trump presented his 2020 plan to end the Israeli-Palestinian conflict, it included the Israeli annexation of swathes of the occupied West Bank, a controversial aspiration that has been revived by his reelection.

In his previous stint as prime minister, Benjamin Netanyahu pushed for partial annexation of the West Bank, but he relented in 2020 under international pressure and following a deal to normalise relations with the United Arab Emirates.

With Trump returning to the White House, pro-annexation Israelis are hoping to rekindle the idea.

Lebanon's new president said on Saturday that Israel must withdraw from his country's south by the January 26 deadline set to fully implement an Israel-Hezbollah ceasefire agreed last year.

His remarks follow a speech by Hezbollah leader Naim Qassem who accused Israel of hundreds of ceasefire violations, warning it against testing "our patience" and calling on the Lebanese state to be "firm" in its response.

A ceasefire in the Gaza war will begin on Sunday morning, mediator Qatar said, as Israeli Prime Minister Benjamin Netanyahu vows to bring back "all the hostages" held in the Palestinian territory.

The truce is intended to end more than 15 months of fighting and devastating bombardment, but in a televised address Saturday evening, the hawkish premier stressed Israel had US support to return to war if necessary.