British police are bracing for violent clashes on Saturday when demonstrators opposed to a state funeral for former Prime Minister Margaret Thatcher may be challenged on the streets by Thatcher supporters, including football fans.

Some cities across Britain have already witnessed bizarre scenes of people dancing and celebrating the death of Thatcher, who passed away earlier this week at the age of 87.

There will be more such “celebrations” to follow, but this time resistance will emerge from outraged Thatcher fans.

The Daily Telegraph reported that leftist groups are planning three rallies to “cheer” Thatcher’s death on Saturday in Trafalgar Square in Central London. These demonstrators will have to contend with about 50,000 football fans exiting a semi-final match between Wigan and Millwall, who have vowed to confront the anti-Thatcher crowd.

On social media networks, football fans have made violent threats.

A Millwall fan wrote on Twitter: "To all you p---- protesting on Sat at Trafalgar sq about [T]hatcher, be warned Millwall [is] in town and in force, expect abuse from me."

Another Millwall supporter warned: "The commies are having a party to celebrate Thatcher dying at Trafalgar Sq Saturday. 30k Millwall fans will be about too in London that day."

On the other side, aside from expressing their distaste for Thatcher, leftists and trade unions will protest spending cuts and welfare changes enacted by the current coalition government and its cabinet ministers.

Rachel Johnson, a member of an anti-government group called UK Uncut, complained: "This government is turning Margaret Thatcher's wildest dreams into a nightmarish reality for ordinary people.”

Police and city officials have urged the public to avoid central London over the weekend.

“Whenever any of these large demonstrations and marches are on, it is always better for the public to keep very clear, because they can get nasty,” said Richard Tracey, a Greater London Assembly member who once served as the Sports Minister under Thatcher.

“There is always the chance that this could cause chaos if one of the events runs into the other. Who knows what could happen as they all seem to get rather tribal.”

If trouble explodes on Saturday, police fear that could harbinger even more trouble for Wednesday when Thatcher’s funeral will be held.

Separately, a London police officer who tweeted offensive remarks about Thatcher has resigned.

Sergeant Jeremy Scott said he wished that Thatcher died a "painful and degrading" death and noted her demise came "87 years too late.”

“The world is a better place today now that c--- is dead,” he added. “Now for [Prime Minister David] Cameron, [Home Secretary Theresa] May and [Chancellor of the Exchequer George] Osborne."