The Dalits, at the bottom of Hinduism's caste system, invited "all those who are discriminated against" -- from the Osus of Nigeria and the Quechuas of Ecuador to the Burakus of Japan -- to unite to end their common suffering.

The appeal came in Bombay at the World Social Forum, the anti-globalisation meeting which began last Friday and is billed as a counterweight to the World Economic Forum which starts this week in Davos, Switzerland.

"The caste system is racist, it rests on discrimination," said Aparna Lanjewar, caste specialist at Bombay University, struggling to be heard above the din of a huge crowd gathered for a seminar on "Discrimination and oppression in the name of race or caste".

The Dalits have been hoping the World Social Forum will help forge an international alliance with other marginalised groups so that discrimination can be tackled globally.

"Your battle is a battle for humanity," said A. Padmanabhan, a high-caste Hindu who runs a group aimed at aiding Dalits.

Even though India outlawed untouchability half a century ago, millions of Dalits still are treated as "unclean" -- denied permission to drink from the same water as higher caste Hindus or worship or live alongside them.

While their plight may be best known internationally, the New York-based Human Rights Watch says at least 250 million people worldwide still live in situations of segregation and servitude.

Participants at the meeting late Monday listened as representatives of the world's outcast communities, such as Victor Dike, champion of Nigeria's Osus, recounted the painful discrimination they endure.

"Osus are social lepers in Nigeria," said Dike, referring to the 1.5 million "excluded" Osus who live in the part of southeastern and south-central Nigeria and are regarded as "subhuman, unclean or slaves".

"One can't drink or eat with them or touch them otherwise one can be transformed into an Osu," Dike told the audience.

From Japan came tales of the difficulties faced by the three million Burakus. "They used to work on dead animals, tanning leather for the Imperial Court during the 17th century and as a result were not considered human", said Tagawa Masato, a member of the Buraku Liberation Movement.

Since then, he said, their situation remains pitiful. "Burakus suffer more frequent unemployment and lower salaries," Masato said, appealing for help from abroad in combating discrimination faced in Japan.

Another speaker, from Ecuador, a Quechua, said the indigenous community had faced discrimination for 500 years. "We're denied the right to education, to work, to dignity -- even to live," said Blanca Chansanco, former president of the confederation of indigenous peoples in Ecuador.

The group heard only once solution -- repeated over and over -- to end their suffering. "Let us join forces," said Nigeria's Dike.