Hundreds of opponents of Margaret Thatcher filled London's Trafalgar Square on Saturday evening for a rain-soaked celebration of the former British prime minister's death earlier this week.

Former coal miners involved in the year-long strike against the Iron Lady's government in the 1980s joined far-left activists and students to drink to the Iron Lady's demise.

An effigy of the former Conservative leader was carried through the crowd beneath Nelson's Column, complete with her trademark string of pearls and bouffant hair made from orange plastic bags.

There was a strong police presence for the demonstration, after trouble erupted at several impromptu street celebrations following Thatcher's death from a stroke on Monday at the age of 87.

But the atmosphere was more street carnival than riot, with people of all ages -- many of them barely born when she left office in 1990 -- dancing, playing tambourines, blowing whistles and horns.

Five people were arrested on suspicion of being drunk and disorderly or for inflicting grievous bodily harm, police said.

Several of those attending said they were also planning to protest at Thatcher's funeral on Wednesday by lining the processional route and turning their backs when her coffin goes past.

The ceremony will fall short of a full state funeral but it will involve 700 members of the armed forces and be attended by the queen among 2,000 global political figures and celebrities.

The former premier's daughter Carol Thatcher earlier said she was bracing for a "tough and tearful week".

The Trafalgar Square event was organised on social media sites and driven by a call two decades ago by some of Thatcher's opponents to hold a party on the first Saturday after her death.

The square is one of London's biggest tourist hubs and the scene of a riot in 1990 against the poll tax, a deeply unpopular local levy which contributed to Thatcher's fall that year.

Among the crowd on Saturday were ex-miners from the north of England, who saw their communities devastated in a wave of pit closures during Thatcher's 11 years in power from 1979 to 1990.

David Douglass, a former miner and member of the National Union of Mineworkers from Yorkshire, said he was "very pleased" at news of Thatcher's death.

He said she was a "terrible woman" and added: "We're absolutely furious at this image that is being presented on television, that the whole country is in mourning."

Sigrid Holmwood, a 34-year-old Scottish artist living in London, came well-prepared for the rain with a special umbrella reading "ding dong" on the front.

A song from the hit musical the Wizard of Oz, "Ding Dong the Witch Is Dead", has become a rallying cry for anti-Thatcher sentiment since her death and has shot up the singles charts this week.

"I came here today, I wouldn't say to celebrate, but protesting against millions of public money being spent on her funeral when there are (government spending) cuts that affect the sick or the disabled," Holmwood told AFP.

Elsewhere on Saturday, some fans of Liverpool football club held up anti-Thatcher banners at a Premier League match reading "We're gonna have a party" and chanted "Maggie's dead, dead, dead".

Thatcher 'left detailed instructions'

Police are mounting a major security operation for Wednesday's funeral, when Thatcher's coffin will be taken to St Paul's Cathedral through streets lined with members of the armed forces.

The ceremony itself will be carried out in line with strict instructions left by the former premier herself, according to the Daily Telegraph newspaper.

It said she requested that Cameron, as prime minister of the day, read a passage from the Bible but did not want any political eulogy. She also asked that her favourite hymns be sung.

Thatcher's 59-year-old twins Mark and Carol were out of the country when their mother died at London's Ritz hotel, where she spent her last months, but returned home this week.

Carol Thatcher told reporters outside the family's plush home in central London on Saturday that she had been moved by the "magnificent" tributes to her mother from around the world.

"I feel like anyone else who has just lost a second parent," she said, referring to the death of her father Denis in 2003.

She added: "I know that this is going to be a tough and tearful week, even for the daughter of the Iron Lady."

Thatcher's death has sparked fierce debate about her legacy in Britain.

Her admirers credit her with helping to end the Cold War and reinvigorating the British economy after decades of decline.

But left-wing opponents accuse her of pushing a ruthlessly individualistic agenda and putting millions out of work with her radical free-market reforms.