Seven people have died amid violent protests involving tens of thousands of protesters from the Dalit (formerly untouchable) community across India.
They took to the streets on Monday to protest against a Supreme Court order that they say weakens a law designed to protect lower caste communities.
Train services have been affected and some main roads have been blocked in a number of states.
The federal government has asked the court to review its decision.
In its ruling, the court had said that the Scheduled Caste and Scheduled Tribe (Prevention of Atrocities) Act, popularly known as the SC/ST Act, had been "misused" in the past, according to a BBC report Tuesday.
Caste violence continues to be a problem in the country. More than 40,000 crimes against lower castes were reported in 2016 alone, according to official statistics.
Dalit leaders said the ruling made them feel "vulnerable".
"The SC/ST Act ensured the protection of Dalits in India by making any discrimination against our community a punishable offence. With this new Supreme Court order, these legal obligations have ended. We're all sad and shocked," said KP Choudhary, the general secretary of an all-India association for lower castes.
In the central state of Madhya Pradesh, senior police officials said that six people had died.
Bans were imposed on large gatherings after protesters blocked railway tracks and set fire to vehicles. A curfew has been imposed in some parts of the state.
One person has also been killed in the northern state of Rajasthan, police said.
In the northern state of Punjab, exams have been postponed and all educational institutions, banks and offices shut. The state government has also suspended internet services until 11:00pm. Hundreds of protesters carrying swords, sticks, bats, and flags forced shops to shut in several cities in the state and public transport is off the road.
There have been further reports of clashes between protesters and police in parts the northern states of Uttar Pradesh, Jharkhand and Bihar.
Dalit organisations also staged demonstrations in the capital, Delhi, but police said there were no report of any violence. However, roads were blocked in the city centre, causing lengthy traffic jams.
Why do Dalits need protection?
Dalits are some of the country's most downtrodden citizens because of an unforgiving Hindu caste hierarchy that condemns them to the bottom of the heap.
Despite the laws to protect them, discrimination remains a daily reality for the Dalit population, thought to number around 200 million.
Traditionally, they have been segregated from the upper castes and are not allowed to attend the same temples, schools or even drink from the same cups as upper caste people. They do not get education and job opportunities, and are often victims of exploitation, abuse and violence.
Lately, activists say that rising aspirations among young Dalits have improved their lives, but this has also increased violence against them by upper caste community members who are unable to accept this.
