The mob broke the lock of the madrasa and entered it, the police said.
A mob that was part of a Dussehra procession in Karnataka's Bidar allegedly broke into a heritage madrasa on Wednesday night, shouted slogans and performed a puja in a corner of the building. A police case has been registered against nine people and four have been arrested. Muslim organisations have threatened protests if no one is arrested by Friday.
Built-in the 1460s, the Mahmud Gawan Madrasa in Bidar is a designated heritage site under the Archeological Survey of India. The structure is also listed among monuments of national importance.
The mob broke the lock of the madrasa and entered it, the police said.
They shouted "Jai Shri Ram" and "Hindu Dharam Jai" slogans, standing on the steps of the madrassa, before moving to a corner to perform a puja. Videos circulating online show a huge crowd on the steps, trying to get inside the building.
Several Muslim organisations from Bidar have condemned the incident and held protests. They have threatened a massive protest after Friday prayers if all the accused are not arrested.
Asaduddin Owaisi, the chief of All India Majlis-e-Ittehadul Muslimeen, hit out at the state's ruling BJP over the incident, accusing it of promoting such incidents to "demean Muslims".
Critics have accused the BJP of turning parts of the state into a crucible for communal experiments. The allegations started after the row over a hijab ban in educational institutions and spiked as Hindu groups insisted on banning Muslim traders from temple fairs.
In August, Ganesh Chaturthi was celebrated at Hubballi's Idgah ground.