Pro-Palestinian demonstrators have marched through central London, with protesters calling for an immediate ceasefire in Gaza and an end to the escalating conflict in the Middle East.
Tens of thousands walked from Russell Square to Whitehall, where speeches took place outside Downing Street.
The event was organised by groups including the Palestine Solidarity Campaign, with people travelling from around the country to take part.
Seventeen people were arrested, the Metropolitan Police said.
The largely peaceful protest comes one year after the 7 October attacks in Israel.
The Metropolitan Police said it was hard to accurately estimate turnout but the protest “appears to be greater than other recent protests”.
The crowd stretched from Downing Street to Trafalgar Square while speakers, including ex-Labour leader Jeremy Corbyn, were addressing demonstrators.
People could be seen carrying Palestinian flags and placards with messages such as “ceasefire now” and “hands off Lebanon”, and chanting “stop the bombing now”.
A counter-protest also took place, with police forming a cordon between the two marches. But a small group broke away from the pro-Palestinian protest and were stopped trying to approach the counter-protest at Aldwych. Three people were arrested after officers intervened.
Conditions were imposed to move the counter-protest group back to Trafalgar Square as it got “too close to the main march and well away from the agreed area”, police said.
Of the 17 arrests, police said three people had been arrested for assaulting an emergency worker, three for assault, eight for public order offences, one for a breach of Public Order Act conditions and two for supporting a proscribed organisation.
The force said one of those arrested for supporting a proscribed organisation was seen wearing what appeared to be a parachute.
It added it was aware of social media posts showing people holding placards with messages of support for Hezbollah – proscribed as a terrorist organisation by the UK government and others – and it was working to find those involved.
Separately, pro-Palestinian supporters were walking through the centre of Edinburgh on Saturday afternoon.
On Sunday, a memorial event will take place in Hyde Park organised by the Board of Deputies of British Jews, the Jewish Leadership Council and other groups.
The war began when Hamas gunmen attacked Israel on 7 October last year, killing about 1,200 people and taking 251 others as hostages.
Israel responded with a military campaign in Gaza that has now killed at least 41,825 people, according to the Hamas-run health ministry.
