Two children from India's lowest caste have been beaten to death by two men after they defecated in public, according to officials and relatives, in the latest case of communal violence in the country.

Key points: The children belonged to what is known as "untouchables" in India's caste hierarchy

The children belonged to what is known as "untouchables" in India's caste hierarchy The murders followed an earlier verbal altercation between the two families, according to police

The murders followed an earlier verbal altercation between the two families, according to police Poor sanitation is one of India's biggest issues

Rajesh Chandel, superintendent of police in Shivpuri, a district in the central state of Madhya Pradesh, told Reuters the children, identified as 12-year-old girl Roshni and her nephew Avinash, a 10-year-old boy, were attacked on Wednesday.

Two men, whom Mr Chandel identified as Hakam Singh and Rameshwar Singh, have been arrested.

"The accused are mentally stable and during the interrogation they have said they committed this crime," Mr Chandel said, adding the investigation was continuing.

It was not possible to reach the accused or their representatives for comment.

The two children belonged to what are known officially as "scheduled castes", but also called "Dalits" or "untouchables" for their position in India's ancient caste hierarchy.

Discrimination on the basis of caste is illegal but still widespread in India, especially in rural areas where hundreds of millions of people live.

Police and Avinash's father, Manoj Balmiki, said the murders followed an earlier verbal altercation between the two families where "casteist slurs" were used by the accused.

"There is a lot of untouchability issues in our village," Mr Balmiki, 32, told Reuters.

"Our children cannot play with their children."

'Open defecation free'

Sanitation has been a top priority for Indian Prime Minister Narendra Modi. ( Reuters: Shailesh Andrade )

Poor sanitation that forces Indians to defecate outdoors is one of the country's biggest health issues, and its eradication has been a top priority for the Bharatiya Janata Party Government led by Indian Prime Minister Narendra Modi.

Mr Modi launched the Swachh Bharat, or Clean India, mission in 2014, and has promised to make India "open defecation free" (ODF) by October 2 this year.

This week Mr Modi was given an award by the Gates Foundation at a ceremony in New York for his role in the scheme.

Swachh Bharat has constructed more than a hundred million toilets for some of the poorest in Indian society, according to official data, but problems in some areas remain.

Anugraha P, a civil servant in the Madhya Pradesh district, told Reuters that Bhaukhedi village, where the two families live, had been declared as ODF in 2018, but that Balmiki's house did not have a toilet.

The caste system has been legally abolished, but is still a significant part of India's culture today. ( ABC News: Jarrod Fankhauser )

Reuters