Protesters hold placards as they walk over Westminster Bridge during a 'March For Palestine' in London on Saturday. AFP

Aerial footage showed large crowds setting off on the march organised by the Palestine Solidarity Campaign, with the protest due to end outside the Houses of Parliament after passing Prime Minister Rishi Sunak's Downing Street office.

Echoing Washington's stance, Sunak's government has stopped short of calling for a ceasefire, and instead advocated humanitarian pauses to allow aid to reach people in Gaza.

Britain has supported Israel's right to defend itself after an Oct.7 attack by Hamas that Israel said had killed 1,400 people, mostly civilians.

"The superpowers at play are not doing enough at the moment. This is why we're here: we're calling for a ceasefire, calling for Palestinian rights, the right to exist, to live, human rights, all our rights," said protester Camille Revuelta.

"This is not about Hamas. This is about protecting Palestinian lives," she added.

London police have faced criticism in recent days for not being tougher over slogans shouted by some protesters during another pro-Palestinian march in the capital last week, which drew about 100,000 people. That protest was mostly peaceful with only a handful of arrests.

Ahead of Saturday's event, police warned there was no place for hate crime and said 2,000 officers would be on duty across the city. Special restrictions were in place restricting protests around the Israeli Embassy.

Reuters