LONDON - Three people have been arrested in a security clampdown related to Prince William's wedding to Kate Middleton, police said Thursday.

The arrests come as Britain's police force gears up for a modern security nightmare in Friday's event at Westminster Abbey, with 5,000 officers on duty to look out for everything from Irish dissident terrorists, Muslim extremists, anti-monarchists, protesters and ordinary riffraff who might blight the royal spectacle.

Scotland Yard said officers detained three individuals in south London Thursday evening on suspicion of conspiracy to cause public nuisance and breach of the peace. The suspects — two men, aged 68 and 45, and a 60-year old woman — remain in custody at a local police station, the Metropolitan Police said.

The police declined to give further details, saying it believed those arrested were planning to attend the royal wedding and that 19 other arrests not specifically related to the event were made in London earlier in the day.

Police have been planning the security operation around the wedding since William's engagement to Middleton was announced in November.

Earlier this week, Scotland Yard Police Commander Christine Jones said there has been no new terror threat to London around the royal wedding but considerable Internet chatter.

"Our operation has been meticulously planned, and we have thought through and planned for a huge range of contingencies," she said.

Thousands of people are expected along the parade route, a snaking path of less than a mile (two kilometres) from the abbey — an iconic cathedral near London's Big Ben and Parliament buildings — to Buckingham Palace, where the new royal couple will appear on the balcony for one of the most anticipated kisses in decades.

A wide range of police will be on patrol Friday: officers on motorcycles, escort specialists, dog handlers, search officers, mounted police, protection officers and firearms units, although only a fraction of Britain's police officers are armed. Security around London's subway network will be boosted, while policing at Heathrow, Europe's busiest airport, will be as normal.

Britain has seen several major terror attacks and plots since the Sept. 11 terror attacks in 2001. The deadliest came in 2005, when homegrown terrorists killed 52 commuters during London's rush hour — Europe's first suicide bombing. In 2006, terrorists in Britain tried to down several trans-Atlantic airliners using liquid explosives. The following year, two major terror plots were thwarted outside a London nightclub and at an airport in Scotland.

London has also seen large protests recently against the Conservative-led government's austerity plans, which aim to cut 310,000 government jobs and sharply hike university tuition fees. Prince Charles and his wife Camilla were shaken up when their car was attacked in December when a student protest turned violent.

A group called Muslims Against Crusades said Wednesday they wouldn't protest the wedding but urged Muslims to stay away from central London and public transport because of the possibility of an attack. Leader Asad Ullah said the warning was general and not based on any intelligence.

Many Muslims have voiced anger over Britain's involvement in the Iraq war and the fact that Prince William's younger brother Harry served in Afghanistan. Prince Harry will be the best man at the wedding.

British police have special stop-and-search powers now if they think people in the crowds are carrying something suspicious. Some 60 people have already been banned from the parade route Friday and both uniformed and undercover officers will be in the crowds or on rooftops.

The wedding guests — kings and queens, sports and entertainment celebrities, charity workers, RAF pilots, and friends and family of the royals — will have their identification checked and go through a security screening before entering the abbey.

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Associated Press writer Paisley Dodds contributed to this article.