An Indian student from the lowest Dalit caste was hacked to death and his wife critically injured in southern India in a suspected "honor killing" by relatives angered by their marriage, police said Monday.

Three men armed with sickles and sharp weapons attacked the 22-year-old student and his wife, who is from a higher caste, on a crowded street in Tamil Nadu state on Sunday.

Police commissioner N Manjunatha said the 19-year-old woman's relatives were angered by the couple's marriage. "They married eight months ago and the woman's family was unhappy. She is an upper Thevar Hindu caste and the man was a Dalit," Manjunatha said.