Jeremy Corbyn was among the speakers at a protest attended by thousands in central London to demand “freedom” for Palestinians.
A large crowd gathered in Hyde Park on Saturday afternoon for a rally in solidarity with the people of Palestine.
Protesters held banners, let off fireworks and chanted despite the heavy rain. A Palestinian flag was also placed at the top of a nearby crane.
Organisers from the Palestine Solidarity Campaign estimated that over 180,000 people attended the rally.
Mr Corbyn spoke at the end of the event, after speeches from former shadow chancellor John McDonnell and rapper Lowkey.
The former Labour leader said: “Children should not grow up having seen their home demolished by a bomb dropped from the safety of thousands of feet above.
“The occupation is the issue, the occupation of the West Bank, the siege of Gaza, they are the issues.
“While the ceasefire is a step forward, unless the fundamental issues are addressed, we will be here again.”
Mr Corbyn added: “We will be here as long as is it takes until the Palestinian people are free.
“We will never give up on the Palestinian people, we will never go away from the Palestinian people and their cause.”
He was welcomed to the stage to large applause and chants of “Oh Jeremy Corbyn”.
Mr McDonnell said: “Yes, a ceasefire has been negotiated and we welcome a ceasefire.
“But let’s be clear, there will be no ceasefire in our campaign to boycott, disinvest and sanction the Israeli apartheid state.
“The message is clear, we will not cease our campaign in solidarity until there is justice.
“So let’s make it clear, no justice, no peace.”
It came after thousands marched through central London from Victoria Embankment on their way to Hyde Park.
They held banners and placards and chanted, blocking off road traffic as they walked.
Some could be seen wearing costumes, masks and face paint, while others were draped in the Palestinian flag.
Groups of police officers watched on, as people climbed bus stops and lampposts and wrote “Free Palestine” on walls.
Chants of “Israel is a terrorist state” and “we are all Palestinians” could be heard as they marched.
One protester, named Muktha Ali, 32, from Harrow, north-west London, told the PA news agency: “I’m here because this is now urgent, the Israeli occupation needs to end now, it’s been long enough.
“Mothers, fathers, brothers, sisters and children have been bombed and murdered, Palestine has to be free.”
Another, named Jake, said: “I stand in solidarity with Palestinians, and so should everyone, no matter your nationality.
“It’s great to see so many people come out in their thousands to support the cause, we will win, our cause will be heard.”
While largely peaceful, a few could be seen throwing objects at police officers who attempted to split up the march after they reached Hyde Park.
The Metropolitan Police confirmed that seven men were arrested during the protests and they have all been taken into custody.
Three of the arrests were for violent disorder, two for going equipped to steal, one for a racially aggravated public order offence and another for a homophobic public order offence, the force said.
Among the groups in attendance were branches of the National Education Union and the Stop The War Coalition.
Saturday marked the first full day of a truce that ended the fourth Israel-Hamas war in just over a decade.
Israel’s security cabinet has approved a ceasefire, a move praised by Boris Johnson and Foreign Secretary Dominic Raab.