Various political parties in Tamil Nadu have been demanding that India boycott the Commonwealth Heads of Government Meeting (CHOGM) to be held in Sri Lanka next month on the Sri Lankan Tamils issue.
Police said the petrol bombs were hurled at the Mylapore and Mandaveli post offices around one am, triggering a blaze that damaged some furniture and electrical appliances.
"We have arrested four persons belonging to the Periyar Dravidar Kazhagam. Their motive seems to be to protest against the Central government over the CHOGM issue," Narendran Nair, Deputy Commissioner of Police told PTI.