The marches reflected growing disquiet in Europe about the mounting civilian casualty toll and suffering from the Israel-Hamas war, particularly in countries with large Muslim populations, including France.
The Palestinian death toll in the Israel-Hamas war has reached 9,448, according to the Hamas-run Health Ministry in Gaza.
In Israel, more than 1,400 people have been killed, most of them in the October 7 Hamas attack that started the war.
At a Paris rally that drew several thousand protesters, demonstrators called for an immediate ceasefire in Gaza.
Some demonstrators also took aim at French President Emmanuel Macron, chanting "Macron, accomplice".
Paris's police chief authorised the march from Republique to Nation, two large plazas in eastern Paris, but said any behaviour deemed antisemitic or sympathetic to terrorism would not be tolerated.
Multiple countries in Europe have reported increasing antisemitic attacks and incidents since October 7.
In the latest incident on Saturday, someone knocked on the door of a Jewish woman in the French city of Lyon and stabbed her twice inthe stomach, according to the woman's lawyer who spoke to broadcaster BFM.
He said police also found a swastika on the woman's door.
The woman was being treated in a hospital and her life was not in danger, the lawyer said.
In Berlin, around 1,000 police officers were deployed to ensure order after previous pro-Palestinian protests turned violent.
German news agency dpa reported that about 6,000 protesters marched through the centre of the German capital.
Eleven people were arrested after thousands of pro-Palestinian protesters gathered in London's Trafalgar Square.
Demonstrators climbed on top of the square's famous fountains as the mostly peaceful group waved flags and banners on Saturday.
But there were scuffles with police as the evening went on, and smaller groups of protesters began moving away from the square.
At least one protester was seen carrying a banner which read "Let's keep the world clean" with a picture of an Israeli flag being thrown into a bin.
A similar banner displayed at a protest in Warsaw was condemned by the Israeli ambassador to Poland as "blatant antisemitism".
Other protesters chanted "from the river to the sea, Palestine will be free", despite controversy around the slogan's meaning.
UK Home Secretary Suella Braverman has previously branded the slogan antisemitic and claimed that it is "widely understood" to call for the destruction of Israel.
However, pro-Palestinian protesters have contested this definition.
Former British Labour leader Jeremy Corbyn and comedian Alexei Sayle were among those who addressed the crowd on a stage set up in the square.
A 24-year-old man was arrested on suspicion of a racially aggravated offence after he was filmed giving a speech, police said.
Protesters also gathered for a sit-in at Charing Cross station, which is near to Trafalgar Square in central London, on Saturday evening.
Earlier in the day, 350 people staged a sit-in protest which shut down Oxford Circus.
The demonstration stopped traffic during the shopping district's busiest hours, following similar disruptive protests at major stations.
It comes after a week of similar disruptive actions at major UK transport hubs.
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