LONDON — Multitudes marched through the British capital on Saturday, as pro-Palestinian supporters made their latest mass call for a ceasefire, with police out in force to prevent clashes with counter-protesters.

The “National March for Palestine,” organized by the Stop the War Coalition, set off after a two-minute silence to remember Britain’s war dead on Armistice Day was observed at The Cenotaph war memorial in central London at 1100 GMT.

Huge crowds of protesters waved black, red, white and green Palestinian flags and held aloft placards proclaiming “Stop Bombing Gaza,” just over a month since Hamas terrorists swept over the border and ravaged Israeli communities, killing more than 1,200 and taking some 240 people hostage.

The Hamas-run health ministry in Gaza says that over 11,000 people have been killed since the war began. The figures cannot be independently verified and are believed to include terror operatives and civilians killed accidentally by Palestinian gunmen in the Strip.

As the march set off, protesters shouted “Free Palestine” and “Ceasefire now.”

London’s Metropolitan Police has made a total of nearly 100 arrests at previous pro-Palestinian marches, including for supporting Hamas, which is proscribed as a terrorist group in the UK, and hate crimes.

But Saturday’s march has generated concern because it coincides with Armistice Day, commemorating the end of fighting in World War I in 1918 — and political criticisms about the policing operation.

Prime Minister Rishi Sunak made a late plea for calm late on Friday, calling for protesters to do so “respectfully and peacefully.”

Met Police deputy assistant commissioner Laurence Taylor said march organizers had changed the route from Hyde Park to the US Embassy in south London to ensure it would not pass any landmark memorials.

Previous events have seen “small groups break away” and “their behavior has been escalating and becoming more violent,” Taylor, who is leading the policing operation, told reporters.

Metal barriers were placed around the area containing the most significant memorials, and an exclusion zone created, with police able to arrest any marchers who try to breach it.

Thousands of people wearing red poppies — the symbol of remembrance — stood heads bowed at The Cenotaph on Whitehall for a solemn ceremony of reflection, with other services held up and down the country.

Minor scuffles broke out near the memorial as counter-protesters — many dressed in black with their faces covered, and some waving England’s St. George’s flag and the Union Jack — tried to break through police lines.

Objects were later thrown at officers in the nearby Chinatown area, the Met said on X (formerly Twitter).

Taylor has said counter-protesters were likely to include groups of football hooligans, and police were “likely” to have to use force at some point against “pockets of confrontation.”

British media reported that Tommy Robinson, the leader of the far-right English Defence League, was among the counter-protesters.

About 1,850 police officers, including some from other forces across Britain, have been drafted in to keep the peace, with 1,375 on Sunday, when a national service of remembrance takes place at The Cenotaph led by King Charles III, senior royals and political leaders.

Home Secretary Suella Braverman, an increasingly outspoken right-winger, has done little to quell tensions, by accusing police of being more sympathetic to the pro-Palestinian protests than others.

Support for Palestinians is a long-standing policy of the British political left.

The government was also at odds with the Met this week, with ministers calling for the march to be banned, sparking concern over political interference in operational matters.

Sunak said he would hold Met Police Commissioner Mark Rowley “accountable” for his decision to allow the demonstration to go ahead.

Rowley has said, however, that it does not meet the threshold for requesting a rare government order to stop it going ahead.

Many of the previous demonstrations featured people glorifying Hamas, calls to destroy Israel and antisemitic incidents.

There have also been a number of incidents of pro-Palestinian and anti-Israel chants by crowds using public transportation as they travel to and from the demonstrations.

“We know the cumulative impact continued protest, increasing tensions and rising hate crimes are having across London and the fear and anxiety our Jewish communities in particular are feeling,” police said in a statement on Friday.

“They have a right to feel safe in their city, knowing they can travel across London without feeling afraid of intimidation or harassment,” police said.

The Metropolitan Police also said that they were working with forces outside London to ensure that any convoys of vehicles arriving in the capital while waving flags and/or shouting antisemitic abuse will be kept away from Jewish communities, noting that if anyone in a convoy commits an offense, that too will be “dealt with.”

In a statement reported by the BBC, Sunak urged on Friday that protesters be “mindful of the fear and distress in Jewish and Muslim communities.”

“Remembrance weekend is sacred for us all and should be a moment of unity, of our shared British values and of solemn reflection,” Sunak said.

London’s The Times reported Saturday that extremist groups would be in attendance at the march, including members of a group seen in a video chanting for an intifada.

The report said the Revolutionary Communist Group (RCG) had held events where speakers declared that Israel has no right to exist, and one said: “All they’ve been doing is yapping about hostages, hostages, hostages… In our lifetime, the flag of Palestine will fly over Jerusalem.”

The newspaper also reported that Ziad El Aloul, a spokesman for Palestinian Forum in Britain which helped organize the protests, shared videos on October 7 “in celebration of the attack ‘by land, air and sea’.”

The report said he has been photographed at the rallies alongside former Labour leader Jeremy Corbyn.

Israel has maintained the stance that Hamas would use a ceasefire to regroup, and that one cannot be implemented without the release of the hostages held by Hamas.

Hundreds of thousands of people have taken part in demonstrations every Saturday since the war began organized by left-wing groups and Muslim organizations. There also have been rallies supporting Israel and demanding Hamas free the hostages it seized in its October 7 onslaught, although those have mainly been attended by members of the Jewish community.