Police have violently clashed with pro-Palestinian protesters close to Downing Street as thousands descended on central London with banners and posters to call for end an to the conflict in Gaza.
Some protesters were chanting "from the river to the sea, Palestine will be free", despite controversy around the slogan's meaning.
Counter demonstrations were also taking place, with dozens of people with Union flags standing close to the Cenotaph on Whitehall, drawing chants of “shame on you” from pro-Palestinian marchers.
Outside the gates of Downing Street, officers appeared to be detaining someone before demonstrators began scuffling with them.
Punches and kicks were thrown and police ordered people to move away.
One man was taken to the floor and carried away to chants of “let him go” from other protesters. Cries of “Allahu akbar”, the Arabic phrase for “God is great” also rang out.
The Metropolitan Police said one person has been arrested after a police officer was assaulted.
The force added an officer was being taken to hospital following the incident on Whitehall.
Another man was arrested in Waterloo Road on suspicion of a racially aggravated public order offence and making threats to kill.Ahead of the march, the Met said it expected up to 100,000 people at the protest but warned officers will intervene if any demonstrators use the word “jihad” in chants.
Kyle Gordon, who is leading the force’s command team, told a press briefing: “If somebody is calling for jihad specifically against Israel the officers will intervene, gather the information, report it back into us and we’ll be working with colleagues (from counter-terrorism) in relation to what the best course of action is.”
It comes after Met commissioner Sir Mark Rowley differed with ministers this week over how to police pro-Palestine protesters using the phrase.
As the demonstration wound to a close, fireworks were "launched at officers from within the crowd" at Trafalgar Square, Metropolitan Police said. The week before, 15 people arrested while nine police officers were injured.
On Friday, Mr Khan and some Labour MPs came together to call for a ceasefire in Gaza.
"Many Londoners like me have watched the absolute horror at the death and suffering in Israel and Gaza," Mr Khan said.
"I join the international community in calling for a ceasefire. It will stop the killing and would allow vital aid supplies to reach those who need it in Gaza."
He was supported by several Labour MPs, including Dawn Butler and Marsha de Cordova.
Brent Central MP Ms Butler said: "I agree with Mr Khan’s statement. An immediate ceasefire is necessary and a freeing of all hostages."
On Saturday, former Labour leader Jeremy Corbyn has addressed pro-Palestine protesters in London .
Speaking on a stage in Parliament Square, he said: “The world’s nations voted at the United Nations last night in the General Assembly by an overwhelming majority to demand a ceasefire.
“It’s not much to ask, a ceasefire, when children are being killed by weapons coming through the rooms of their homes.
“It is in eternal stain that the British Government abstained on that vote.”