The rally in Trafalgar Square will remember the 1984 attack on Golden Temple Sikhs from across the UK have begun a march through central London to mark the anniversary of an attack on their holiest shrine in India.
The Remembrance March from Hyde Park to Trafalgar Square is to commemorate the 1984 attack on the Golden Temple in Amritsar, Punjab, north India.
Indian armed forces stormed the holiest Sikh shrine 27 years ago to flush out militants from the temple premises.
Leaders will also call for the right to self-determination at the rally.
The Sikh Federation UK, which organised the event, said they expected up to 25,000 people to attend the Freedom Rally at Trafalgar Square.
Organisers said Liberal Democrat MP Simon Hughes and Green MP Caroline Lucas were expected to speak at the rally which will also be addressed by leaders from the Sikh community in the UK and Europe as well as representatives from India.
The attack on the temple complex – Operation Bluestar – had been personally approved by Indian Prime Minister Indira Gandhi, to flush out militants who wanted an independent homeland of Khalistan.
There has never been agreement on the numbers killed, but Sikhs say thousands were massacred by Indian troops, many of them innocent bystanders.
Mrs Gandhi was assassinated four months later by her Sikh bodyguards. Following her death anti-Sikh rioting erupted in India which left about 3,000 Sikhs dead.
Events are also being held in Vancouver in Canada and in California to mark the 27th anniversary of the attack.
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