Thousands attended the conversion ceremonies in Nagpur

The events in the central city of Nagpur are part of a protest against the injustices of India's caste system, activists say.

The Dalits - once known as Untouchables - hope to escape the prejudice and discrimination they often face.

Laws designed to protect Dalit rights are ineffective, critics say.

The ceremonies mark the 50th anniversary of the adoption of Buddhism by the scholar Bhimrao Ramji Ambedkar.

He was the first prominent Dalit to urge low-caste Indians to embrace Buddhism.

As the chief architect of India's constitution, he wrote anti-discrimination provisions and quota systems into the country's law.

'Cry for dignity'

The Dalits arrived by the truckload at a public park in Nagpur for ceremonies, which began with religious leaders giving fiery speeches against the treatment of lower castes.

DALIT FACTS 167m people, 16.2% of India's population Nearly 60% live in Uttar Pradesh, West Bengal, Bihar, Andhra Pradesh, and Tamil Nadu states The lowest rank in Hindu society, beneath the traditional caste system Expected to perform the most menial jobs, particularly handling cadavers and human and animal waste Physical contact with a Dalit was traditionally considered ritually polluting for other castes Even converts to Christianity and Islam have encountered discrimination from higher-caste converts

Reuters reported that dozens of riot policemen had turned out at the sprawling park.

Udit Raj, a Dalit leader, told the BBC that around 2,500 people converted to Christianity and Buddhism.

Joseph D'Souza, the president of the Dalit Freedom Network and a Christian convert, described the conversions as a "celebratory occasion".

"I think it's important to understand that this is a cry for human dignity, it's a cry for human worth," he told the BBC.

He said that Dalits could seek dignity by converting to Christianity, Jainism or Sikhism as well as Buddhism.

Laws against conversion

Several states governed by the Hindu nationalist party, the BJP, have introduced laws to make such conversions more difficult.

Hundreds of Dalits converted to Christianity and Buddhism

The states of Rajasthan, Madhya Pradesh and Tamil Nadu have all passed laws restricting conversions.

Gujarat has reclassified Buddhism and Jainism as branches of the Hindu religion, in an attempt to prevent conversions away from Hinduism eroding the BJP's bedrock support.

Officially, caste discrimination was outlawed when India gained independence in 1947, but many of the country's 180m Dalits say that people's attitudes towards them remain the same.