Britain's prime minister and the mayor of London warned Monday that abuse directed at immigrants wouldn't be tolerated, after a series of incidents were reported following the country's decision to leave the European Union.

Social media have been filled with reports of harassment of EU nationals, particularly Poles, residing in Britain. Some people living in Britain legally complained they were told to go back to their countries.

A spokeswoman for Prime Minister David Cameron said he raised the abuse at a Cabinet meeting Monday. Helen Bower said the prime minister condemned "some of the incidents we have seen across the country over the weekend of intimidating migrants and telling them that they need to go home."

London Mayor Sadiq Khan asked Metropolitan Police to be "extra vigilant" to prevent any incidents.

"It's really important we stand guard against any rise in hate crimes or abuse by those who might use last week's referendum as cover to seek to divide us," he said.

Police are investigating vandalism at a Polish cultural center in west London and incidents in Cambridgeshire in which cards were given to Polish residents telling them to leave the country.

Poland's ambassador to Britain, Witold Sobkow, said on the embassy website Monday that he is "shocked and deeply concerned by the recent incidents of xenophobic abuse directed against the Polish community and other UK residents of migrant heritage."

Immigration from other EU countries played an important role in the referendum campaign, with proponents of leaving the EU arguing doing so would give Britain control over its borders.

A majority of Britons voted to quit the 28-nation bloc on Thursday.