LONDON (AFP) - A couple accused of keeping three women as slaves in a London house for 30 years are of Indian and Tanzanian origin and two of the victims were part of a political "collective", police said on Saturday.

The two older victims involved in Britain's most notorious case of modern-day slavery are thought to have met the male suspect through a "shared political ideology" and began living with him as part of a collective, London's Metropolitan Police said.

The third victim, a 30-year-old woman, is believed to have spent her entire life in servitude in a case that has stunned Britain.

Police commander Steve Rodhouse said the couple, both aged 67, were of Indian and Tanzanian origin and had been living in Britain since the 1960s.

"We believe that two of the victims met the male suspect in London through a shared political ideology, and that they lived together at an address that you could effectively call a 'collective'," he told reporters.

"Somehow that collective came to an end and... the women ended up continuing to live with the suspects."

Police carried out house-to-house enquiries on Saturday, speaking to residents living near the house where the women were held in south London.

The exact location has not been revealed but the police operation centred on a modern, low-rise block of flats in Peckford Place in Brixton, an area known for its vibrant nightlife and large Afro-Caribbean community.

Crowds of journalists gathered at the scene, two days after police first disclosed that the women had been rescued and their two alleged captors arrested as part of an investigation into slavery.

BOUND BY 'INVISIBLE HANDCUFFS'

The victims are a 69-year-old Malaysian, a 57-year-old Irish woman and the 30-year-old Briton.

They were freed on Oct 25 after one of them made secret telephone contact with a charity.

Their alleged captors, who are suspected of immigration offences as well as involvement in forced labour, have been provisionally freed until January pending further investigations.

"The people involved, the nature of that collective and how it operated is all subject to our investigation and we are slowly and painstakingly piecing together more information," Mr Rodhouse said on Saturday.

"The 30-year-old woman does have a birth certificate - however, that is all the official documentation we can find. We believe she has lived with the suspects and the other victims all her life, but of course at this early stage we are still seeking out evidence," he added.

Police said the women had been beaten and brainwashed, but they are not believed to have been sexually abused.

Mr Rodhouse said on Friday that police had uncovered a "complicated and disturbing picture of emotional control over many years".

The women were occasionally able to leave the house, and detectives are trying to understand the "invisible handcuffs" that were used to control them.

They were freed after the Irish woman made secret telephone contact with the Freedom Charity - which normally deals with forced marriage and honour-based abuse - after seeing its work on a television programme.

The case has sparked national soul-searching amid fears it could be the tip of an iceberg.

Ms Aneeta Prem, founder of the Freedom Charity, said its helpline had received "an extraordinary rise in calls" since the story was made public.

"We received five times as many calls in 24 hours as we normally do in one week and are needing to increase our resources to cope with this extra demand," she said.

She stressed that the three victims must be allowed "to go through their rehabilitation undisturbed, without being identified".

Following telephone contact, the British and Irish female victims agreed to meet charity workers and police outside the house, before taking them back to rescue the Malaysian.

Specially-trained officers are now working with the women to try to understand what happened to them, while all 37 officers in Scotland Yard's Human Trafficking Unit are working on the investigation.

The couple had been previously arrested during the 1970s, police revealed on Friday, without specifying on what charges.