Anti-immigrant leaflets saying "Leave the EU - no more Polish vermin" were put on cars near a school, local police said, the day after the country voted to leave the European Union.
On Sunday, the Polish Social and Cultural Association in Hammersmith, west London, was allegedly vandalized with a racist slogan.
Conservative politician and lawyer Baroness Sayeeda Warsi, who quit the "Leave" campaign shortly before the vote, told Sky News that organizations working with race crime victims had seen a rise in reports of abuse since the Brexit vote.
"I've spent most of the weekend talking to organizations, individuals and activists who work in the area of race hate crime, who monitor hate crime and they have shown some really disturbing early results from people being stopped in the street and saying look, we voted Leave, it's time for you to leave," she said.
"They're saying this to individuals and families who have been here for three, four, five generations. The atmosphere on the street is not good."
Warsi had previously accused the "Leave" campaign of peddling "lies, xenophobia and the politics of hate" following her decision to quit before the vote.
Police investigate hate crimes
Cards abusing Polish migrants in both English and Polish were left on cars and at properties around Huntingdon in Cambridgeshire, local police said.
Resident Kathleen Gaynor said she had found one on her mother's doorstep, held down with a stone.
"We were really upset and angry, as she has some really nice Polish neighbors," she told CNN. "There were other cards near schools, in the communities with Polish people living in them and by the riverside in Huntingdon, so they had been put all over the place."
In a statement, Cambridgeshire Detective Superintendent Martin Brunning said police were working with the Polish community and warned that anyone caught distributing racist leaflets could face up to seven years in prison.
There has been a sharp increase in hate crime reporting recently to True Vision, the UK-police funded website designed to provide the public with information about hate crimes, the National Police Chiefs' Council reported Monday.
Eighty-five such incidents were recorded between Thursday and Sunday, compared with 54 reports the corresponding four days last month, according to the NPCC. The agency says this development shouldn't be regarded as a national increase in hate crimes. But it is surely an increase in reporting through this one mechanism, the NPCC said.
"Any reports of hate crime in the county will be fully investigated and it is vitally important that anyone who has received these leaflets or suffered similar abuse reports it," he said.
In London, the Polish and Social Cultural Association woke on Sunday morning to find their front doors sprayed with an abusive message.
Using the hashtag #postrefracism, social media has highlighted alleged incidents of migrants in the UK being verbally insulted and threatened since the final outcome was announced.
Dozens of British social media users have taken to Twitter and Facebook to report incidents of racial abuse, both verbal and physical, across the country in the wake of the European Union referendum.
"We were very disturbed and upset this morning to find really unpleasant graffiti all across the front of our building when our staff came in," the Association's Chair Joanna Mludzinska said in a video on Twitter.
"The police are investigating it as a racially motivated crime but we have been very moved and are extremely grateful to our local counsellors and MPs and our neighbors who've (given their support)."
Many on social media expressed disgust at the attacks with others offering support to migrants living in the UK.
David Matthews @Britabroad90 tweeted: "Just read a tweet about small polish girls crying at UK school at fear of being deported. This really upsets me."
And another social media user called Imi @MyNameIsImi posted: "Dear Polish, Romanians, Latvians, Pakistanis and Iranians living in this country... I'm sorry. I'm so sorry."
Others are worried about a possible trend emerging, not just in the UK but across Europe where some right-wing parties are calling for their own referenda on EU membership following the Brexit decision.
Stephen Colebourne @jodastephen said casual racism in the UK was going unchallenged.