London, like other Western cities, has seen regular and sometimes large demonstrations calling for an end to Israel’s bombardment of the besieged strip.
Police clashed with the protesters, who occupied surrounding roads after they were prevented from marching across Westminster Bridge, where they had planned to unfurl banners.
Police said they had imposed a legal order limiting the location of the protests and that by 3pm (15:00 GMT) people had begun to disperse. Those who refused to comply with an order to leave could be arrested, police said.
Saturday’s action, the first major demonstration of the new year, was smaller than previous mass marches but comes two days before the UK Parliament returns to work after its Christmas break.
The protest was designed to push politicians to adopt a harder stance towards Israel in its war on Gaza, which has killed more than 22,700 Palestinians in three months.