Boris Johnson has condemned acts of "shameful racism" as police investigated video appearing to show anti-Semitic language being shouted from a convoy of cars in London.
Footage on social media showed a convoy of cars covered with Palestinian flags passing down Finchley Road, in north London, with passengers heard to shout offensive language and threats against Jews.
The Metropolitan Police said they were aware of the incident in the St John's Wood area and were carrying out urgent enquiries to identify those responsible.
"This sort of behaviour will not be tolerated," the force said.
The footage, along with other incidents that have emerged following large pro-Palestine rallies over the weekend, has received cross-party criticism.
Mr Johnson said: "There is no place for anti-Semitism in our society.
"Ahead of Shavuot, I stand with Britain's Jews who should not have to endure the type of shameful racism we have seen today."
Labour leader Sir Keir Starmer described the incident as "utterly disgusting."
"Anti-Semitism, misogyny and hate have no place on our streets or in our society," he said.
"There must be consequences."
Referring to the video of the convoy, Housing and Communities Secretary Robert Jenrick said: "This, on the streets of London, is deeply disturbing.
"Vile, criminal hatred like this must not be tolerated."
Cabinet minister Michael Gove described another video appearing to show protesters shouting anti-Semitic abuse as "deeply concerning".