There is massive anger in Tamil Nadu, where a statue of Periyar was vandalized hours after BJP leader H Raja suggested it in a controversial Facebook post responding to anger over Lenin statues being razed in Tripura.

A petrol bomb was thrown at a BJP office in Coimbatore by three bikers in the early hours today. No one was hurt.

A Syama Prasad Mookerjee bust was also damaged with a hammer in Kolkata; six Jadavpur University students, said to be part of an ultra-left group, have been arrested. Syama Prasad Mookerjee was the founder of the BJP's predecessor Jana Sangh. BJP workers in Bengal took out protests on the streets of Kolkata against the vandalism.

A statue of BR Ambedkar, the architect of the Constitution, was also damaged in Meerut in Uttar Pradesh.

The cycle of vandalism began after two statues of Lenin were demolished in Tripura yesterday, allegedly by workers of the BJP, which defeated the Left in the northeastern state on Saturday.

Apparently justifying the Tripura incidents, BJP leader H Raja suggested on Facebook that Periyar statues in his state could be next. "Who is Lenin and what is the connection between Lenin and India? What connection has India with Communists? Lenin's statue has been removed in Tripura. Today it is Lenin's statue in Tripura, tomorrow it will be the statue of caste fanatic EVR Ramasamy," said the post, which the BJP leader deleted and later disowned after a huge backlash in Tamil Nadu.

H Raja today "expressed regret" for his post and said: "Vandalising Periyar statues unacceptable. Facebook admin posted that message without my permission. My intention was not to hurt anyone."

H Raja's retreat came around the same time BJP president Amit Shah posted his disapproval on Twitter. "I have spoken to the party units in both Tamil Nadu and Tripura. Any person associated with the BJP found to be involved with destroying any statue will face severe action from the party," he posted. But Mr Raja will not face any action for now.

Social activist Periyar is a deeply revered figure in Tamil Nadu; he started the Self-Respect Movement and Dravidar Kazhagam, one of the first Dravidian outfits in the country.