India’s Supreme Court is due to make a long-awaited ruling on a disputed religious site in the northern holy city of Ayodhya.
Officials have appealed for calm and thousands of police and paramilitary troops have been deployed in the city, in Uttar Pradesh state.
Hundreds of people were detained on Friday amid fears of violence.
Hindus and Muslims have for decades been bitterly divided over the 16th Century Babri Masjid mosque in Ayodhya.
The court case centres on the ownership of the land and has been dragging on in the Supreme Court for years.
Hindus believe that the site of the mosque is the birthplace of one of their most revered deities, Lord Ram. Muslims, however, say they have worshipped there for generations.
Provincial police chief Om Prakash Singh told Reuters news agency that social media platforms were being monitored for inflammatory posts ahead of the verdict.
“We will not tolerate Hindus or Muslims publicly displaying their reaction to the court verdict,” he said.
Government departments say they have also made preparations to deal with any violence.