Troops have been deployed in the Indian city of Calcutta after protests over a controversial writer turned into riots.
Hundreds of soldiers are trying to keep peace in Calcutta
Police using tear gas and baton charges were unable to control crowds calling for Bangladeshi feminist writer Taslima Nasreen to leave India.
Rioters blocked roads and set cars alight. At least 27 people were hurt. More than 100 arrests have been made.
Crowds were also protesting at recent attacks on Muslims in the Nandigram area in the east of West Bengal state.
A number of people have been killed and thousands left homeless in Nandigram after violence over now-abandoned state plans to industrialise farm land in the area.
Wednesday's trouble in the state capital began after the predominantly Muslim All-India Minority Forum called for blockades on major roads in the city.
The group said Ms Nasreen had "seriously hurt Muslim sentiments". Many Muslims say her writing ridicules Islam.
Police arrived in strength to disperse the demonstrators.
Violence then broke out in Ripon Street in the north of the city and spread to Park Circus, Moulali and many other areas of central Calcutta.
The BBC's Subir Bhaumik in Calcutta says he saw two army columns, one in Park Circus and one in Moulali.
For most of the day, parts of the city centre were a no-go area, with main roads closed to traffic and commuters stranded.
Children spent hours in buses before they could be returned to the safety of their schools.
"The protesters started pelting policemen with brick bats and acid bottles in several places, so we can say the trouble making was planned and co-ordinated," Calcutta police chief Gautam Chakrabarty said.
Idris Ali, a senior leader of the Minority Forum, blamed the state's ruling Communists for the violence.
"They have infiltrated our ranks and sparked the violence. We wanted to protest peacefully but the Marxists are trying to discredit us," Mr Ali told the BBC.
The Marxists denied the charge.
"We had no idea of their plans, they have planned the trouble, they must take the blame for this mayhem," Communist Party of India (Marxist) leader Biman Bose said.
The All-India Minority Forum says Taslima Nasreen's Indian visa should be revoked and she should be forced to leave the country.
Ms Nasreen faced death threats in her homeland
Critics say she called for the Koran to be changed to give women greater rights, but she vehemently denied making the comments.
Ms Nasreen fled Bangladesh in the early 1990s after death threats and has spent the last three years in Calcutta after a long stay in Europe.
India has not granted her citizenship which she has requested but has granted regular visa extensions.
Minority Forum leaders accuse West Bengal's government of "red terror" in the Nandigram enclave, a troubled cluster of villages to the south-west of Calcutta.
The state government denies it has failed to protect the people of the area from attacks by its supporters.