Two men were arrested on Saturday at a pro-Palestinian Arab march in London, Sky News reported.
One of the men was taken into custody for carrying a swastika emblazoned placard and another for allegedly making racist remarks towards counter-protesters, the Metropolitan Police said.
The arrests come a week after a row erupted over a video that appeared to show a police officer preventing a counter-protester crossing a road near a pro-Palestinian march in London on April 13.
On Saturday, thousands gathered for the Palestine Solidarity Campaign (PSC) demonstration in the capital to call for an immediate ceasefire in Gaza, according to Sky News.
There was also a simultaneous static demonstration organized by pro-Israel group Enough is Enough, which took place along the route of the pro-Palestinian Arab march.
Shortly before 1:00 p.m., Scotland Yard said officers had arrested a man carrying a swastika placard at Parliament Square, where the PSC march set off.
It later said another man was being held for shouting a "racist remark" towards Enough is Enough protesters on Pall Mall.
Chants of "Stop bombing Gaza, stop bombing children" were sung by the crowds and placards saying "Free Palestine, smash the racists" were displayed during the protest.
Protesters could be heard chanting, "From the river to the sea, Palestine will be free".
The PSC march was the 13th national protest since the first was staged on October 9, two days after the Hamas attack on Israel.