The protest, which swelled beyond initial expectations, was organized by the Palestine Solidarity Campaign and other activist groups.
The Palestine Solidarity Campaign said: "10,000+ people at Downing Street now for Palestine as Israel continues its brutal attack on Rafah. Our gov't and the Labour leadership have provided support for Israel as it commits genocide. They have blood on their hands. They must call for a ceasefire now and stop arming Israel."
Due to the unexpectedly large turnout, the Metropolitan Police closed Whitehall to traffic to accommodate the demonstrators.
The police have directed protesters to disperse by 8 p.m. local time, after which Whitehall will be reopened.
Tension arose between activists staging a sit-in protest in support of Palestine and the police in front of the Prime Minister's Office at Number 10.
A brief scuffle broke out between the protesters and the police, who threatened them with detention. The demonstrators linked arms to form a human barrier.  
'Are you going to be a voice to end arms trade with Israel?'
During his address to the crowd, Former Labour Party leader Jeremy Corbyn called for an end to the arms trade with Israel during a massive protest in Central London.
In a passionate speech, Corbyn questioned the commitment of political leaders: "So, in this fevered political time, the question for anyone that wants to hold public office is, are you going to be a voice to end the arms trade with Israel? Are you going to stop the bombardment of Gaza?"
"This massive movement that's come together, all over the country and all over Europe, all over the world, supporting the Palestinian people, makes a difference. It also makes a difference to be a voice for a different world—a world of peace, not a world dominated by the arms industry and the cynical calculations of military planners. Instead, a world where we look to the needs and hopes of the poorest people, the most desperate people, and we pass nobody by on the other side. Our watchword is peace, is justice, is unity," he said.  
'I don’t watch any Western media anymore'
Among the attendees was Hannah, a frequent participant in such protests, who expressed her frustration, saying: "I've been coming to all of the marches since they started, but what’s happening now is beyond words. Netanyahu’s propaganda is terrifying. I made a placard today about the media’s role in this. I don’t watch any Western media anymore; I follow Al Jazeera and Middle East Eye because the Western media is just spreading lies. He (Netanyahu) says it was a mistake, but he’s been bombing and targeting healthcare workers, civilians, children, schools, and hospitals for years, not just since Oct. 7. It’s horrifying that the media isn’t representing the truth."
Another protester, Tyne, shared his outrage, saying: "Not just in the past eight months, but Israel has always committed atrocities against Palestinians. The willingness to bomb and decimate a beautiful country and its people, especially children, is terrifying."
"It wasn’t just last night; all the content I’ve seen makes me weep. I refuse to turn away because I can’t believe this goes unchallenged by any democratic parties around. We must stand on the streets every day because Israel is an occupying state that has never had legitimacy. They shouldn’t have been given that in 1948 anyway," she added.
Israel launched an airstrike Sunday on a camp for displaced people in Rafah that killed at least 45 people, mostly women and children.
Israeli tanks have been seen in central Rafah for the first time, signaling a new phase of its brutal offensive in which more than 36,000 Palestinians, mostly women and children, have been killed and over 80,000 injured amid mass destruction and shortages of necessities in Tel Aviv’s onslaught against Gaza.
The assault has pushed 85% of Gaza’s population into internal displacement amid acute shortages of food, clean water and medicine, while 60% of the enclave's infrastructure has been damaged or destroyed, according to the UN.
Israel is accused of genocide at the International Court of Justice. An interim ruling ordered Tel Aviv to stop genocidal acts and take measures to guarantee that humanitarian assistance is provided to civilians in Gaza.
Meanwhile, Norway, Spain and Ireland formally recognized Palestine as a state on Tuesday, in what Spanish Prime Minister Pedro Sanchez described as a "historical decision."