Scotland Yard insists raids on squats across London that saw 20 people arrested were not driven by fears that anarchists will try to disrupt the Royal Wedding.

Photographs of a raid on Grow Heathrow, a market gardening project based on squatted land near what would have been the west London airport's third runway, were posted on the Indymedia website

The Metropolitan Police have insisted a string of raids on illegal squats across London in which 20 people were arrested are not connected to security concerns surrounding the Royal Wedding.

Officers made at least three raids on Thursday morning at squatter sites connected with anarchist and environmental protest groups.

Scotland Yard said last week that it would take pre-emptive action, which could include breaking up squats, if there was evidence a group was planning to commit a criminal act. But police insisted Thursday's raids were not part of the security arrangements surrounding Friday's wedding.

A spokesman said: "Police have today executed warrants at three addresses in London as part of an intelligence-led operation.

"Nineteen people were arrested for abstracting electricity at Camberwell Road. One person was arrested at the address in Hackney in connection with the disorder following the TUC march. There were no arrests at the address in Sipson.

"Those arrested are in custody at various London police stations.

"These arrests are part of ongoing proactive work to tackle suspected criminality. They are not specifically related to the Royal Wedding but have been brought forward ahead of the event."

Six people wanted in connection with violence during last month's anti-cuts TUC marches have been arrested in recent days amid fears they could be planning similar disruption.

Met Police officers arrested a further six people at a squat in Hove, east Sussex, on Wednesday. Four were bailed with conditions that did not include any reference to London or the day of the wedding. A man arrested in connection with the TUC March in London last month was taken to London for questioning.

Some 68 people who have been arrested at past demonstrations including the TUC protest and the demonstration against the introduction of student fees, have been banned from Westminster as part of their bail conditions.

A thinly veiled call for anarchists to disrupt the celebrations of Prince William's marriage to Kate Middleton outside Westminster Abbey has been issued on websites like the Black Bloc Facebook page.

It's not Royal Wedding-related, but it is related to the student and TUC demonstrations. Metropolitan Police spokesman

A statement attributed to activists John Shepherd, Susan Petal and Ingrid Muller said: "Our original intention was to stage a protest along the route of the royal wedding in the form of a mass assembly, but we now know that unless we receive permission from the Met Police this would constitute an offence.

"We can no longer BE SEEN to support or encourage such an assembly; nor can we even BE SEEN to present this event as a 'protest' or an 'assembly'. This is because we are intent on BEING SEEN to obey the law.

"However, as 'individual spectators' we are legally entitled to join the crowds gathered on the day to watch the Royals and their privileged guests as they exit Westminster Abbey."

Protesters are planning to meet on Friday morning in Trafalgar Square before heading to Westminster Abbey.