ITV News Security Editor Rohit Kachroo reports
Police are on a heightened state of alert following a spike in hate crimes following the EU referendum.
Mayor of London Sadiq Khan asked Scotland Yard to be "extra vigilant" for any rise in cases.
His appeal came as:
Poland's ambassador expressed shock at "xenophobic abuse" against the Polish community
David Cameron condemned incidents of abuse and hatred targeted towards migrants
The National Police Chiefs' Council revealed there was a 54% increase in hate crimes reported from Thursday to Sunday last week, compared to the corresponding period last month
Boris Johnson said he was "appalled" by reports of an increase in crimes relating to racism and xenophobia
Mr Khan has asked residents to "pull together and rally behind this great city", before adding it was important to not "demonise" the 1.5 million people in London who voted for Brexit.
He said: "While I and millions of others disagreed with their decision, they took it for a variety of reasons and this shouldn't be used to accuse them of being xenophobic or racist.
"We will have a zero-tolerance approach to any attempt to hurt and divide our communities", before adding it will be a priority for the Metropolitan Police to "guard against any rise in hate crime."
ITV News spoke to Zehra Zaidi, a lawyer and policy consultant from Gloucester, who was advised to close her social media accounts by her friends after receiving "hourly" abuse online following the referendum:
Cambridgeshire Police is investigating reports that cards reading "Leave the EU - no more Polish vermin" were allegedly delivered to members of the Polish community in Huntington on Saturday.
The Polish ambassador to Britain, Witold Sobkow, said: "We are shocked and deeply concerned by the recent incidents of xenophobic abuse directed against the Polish community and other UK residents of migrant heritage."
Scotland Yard is also investigating an incident of "racially motivated criminal damage", after offensive graffiti was found on a Polish Centre in Ravenscourt Park, west London.
The Metropolitan Police confirmed high visibility foot patrols have been stepped up in the area.
Addressing parliament on Monday, Prime Minister David Cameron said he spoke to his Polish counterpart, Beata Szydło, to reassure her that "everything is being done" to protect Polish migrants.
The NSPCC said 85 reports were made to True Vision, an online hate crime reporting site, between Thursday and Sunday - an increase of 57% on the corresponding days last month.
The national lead for hate crime, Assistant Chief Constable Mark Hamilton, said: "At the national level, the vast majority of people are continuing to go about their lives in safety and security and there have been no major spikes in tensions reported.
"However, we are seeing an increase in reports of hate crime incidents to True Vision.
"This is similar to the trends following other major national or international events. In previous instances, crime levels returned to normal relatively quickly but we are monitoring the situation closely", he added.