A rights group says hundreds of thousands of Indians are still working with their bare hands and crude tools to clean human excrement from open roads, train tracks and millions of dry pit latrines, despite Indian laws prohibiting manual scavenging.

Human Rights Watch says India's ancient and deep-rooted patterns of caste discrimination are preventing scavengers from escaping their traditional work as waste cleaners.

Scavenging has traditionally been carried out by a sub-group of the dalits, an outcast community also known as "untouchables" within India's ancient system of caste hierarchies. They are often impoverished, shunned by society and forbidden from touching Indians from other castes or even their food.

The New York-based group urged India's government to ensure laws against manual scavenging are implemented nationwide.