Flyers promoting illegal mass gathering 'protests' at 60 UK locations are being shared online across conspiracy theory groups.
Anti-vaxxers and other fringe communities are promoting the mass gatherings which are allegedly taking place in protest over the coronavirus lockdown measures.
In the posters circulating on social media over the past few days, the organisers have boasted the events will be the 'largest mass gathering since the lockdown'.
Dozens of posters with different locations have been shared around the country with the message: "Bring a picnic, some music and let's have some fun and say yes to life."
Some appear to have been photoshopped and suggest more than one 'protest' location in certain cities.
The actual 'organiser' is not clear but it is believed to be linked to the 'UK Freedom Movement' (UKFM) Facebook page.
UKFM, which has existed on Facebook since August 2011, said it is 'committed to exposing the truth regarding global affairs and how the few control the many'.
The apparent gatherings have been promoted on flyers in London, Manchester, Southampton, Nottingham, Sheffield, Cardiff, Edinburgh, Plymouth and Barnstaple in Devon.
The legitimacy of the flyers has not been verified.
However police forces are taking them seriously, with Nottinghamshire saying it has 'contingency' plans in place and Hampshire confirming it is 'reviewing' information it has received.
The posters are headlined 'UK Mass Gathering' said: "We say no to the coronavirus bill, no to mandatory vaccines, no to the new normal and no to the unlawful lockdown."
In Nottingham, police officers will be in attendance at Wollaton Park and Forest Recreation Ground where mass gathering are said to be being planned.
Nottinghamshire Police chief constable Craig Guildford said: "We are aware of the social media coverage which includes Southampton, London and Cardiff as well.
"We are planning, as a contingency, with our partners in the city council as we monitor the situation.
"Should any individual endanger the public by not obeying social distancing the police at the scene will be taking positive action to protect the public."
A Hampshire Constabulary spokesman said: "We are currently reviewing information we have received regarding a mass gathering being organised in Southampton this coming weekend.
"We are really grateful to those who contacted us about this and we will continue to assess the information we have in the coming days.
"Our response will be in line with the Health Protection (Coronavirus, Restrictions) (England) Regulations 2020 which currently prohibits large gatherings of people to limit the spread of Covid-19."
Government guidance on mass gatherings still says such gatherings should not take place. The current advice says: "In line with the social distancing guidance it is advised that large gatherings should not take place.
"While the risks of transmitting the disease at mass gatherings are relatively low, these steps will also allow emergency services that would have been deployed for these events to be prioritised in alleviating pressure on public services."
The starting point for lockdown fines in England will rise to £100 from today.
