At least six people have died in the worst violence to hit Indian Prime Minister Narendra Modi's home state in more than a decade.
Authorities in western Gujarat state on Wednesday said the army had been deployed to try to restore peace after a mass rally turned violent, with protesters torching cars, buses and police stations.
The violence appears to have been triggered by the detention of the 22-year-old leader of a mass movement by the Patidar or Patel caste, which is demanding preferential treatment for jobs and university places.
Director general of police PP Pande told AFP three people were killed in the main city of Ahmedabad, where an estimated half a million people gathered for a rally on Tuesday.
The violence later spread to other parts of the state and another two people were killed when police opened fire on rioters early on Wednesday in Banaskantha district, and a sixth protester died in Mehsana district, also in police firing.
A police constable, who was beaten by a mob, and two others injured in the rioting, succumbed to injuries in hospital late on Wednesday.
"I appeal to all brothers and sisters of Gujarat that they should not resort to violence," Modi said in a television address delivered in his native Gujarati.
"Violence has never done good for anyone. All issues can be resolved peacefully through talks," said Modi, who served as the state's chief minister for more than a decade.
The Patidars or Patels are one of the state's most affluent communities, but they say they are struggling to compete with less privileged castes for jobs.
India sets aside a proportion of government jobs and university places for Dalits, known as "untouchables", and for so-called "other backward castes" under measures intended to bring victims of the worst discrimination into the mainstream.