The chief minister of the Indian state of Tamil Nadu has called for federal police to investigate a deadly petrol bomb attack on a newspaper office.
The newspaper office was targeted for publishing a survey
Three people died when protesters set fire to the daily Dinakaran's office in the town of Madurai on Wednesday.
The protesters were angry at a survey in the paper which found their leader MK Azhagiri to be less popular than his brother and political rival MK Stalin.
The two are sons of veteran politician and state Chief Minister M Karunanidhi.
All three belong to Tamil Nadu state's governing DMK party.
What people think?
As the family feud spilled out into the open, the chief minister said he had called for a investigation into the attack by the Central Bureau of Investigation (CBI).
Police said they had made several arrests in the case.
Officials said a mob, armed with stones and petrol bombs, attacked the newspaper office on Wednesday, killing three employees.
Mr Karunanidhi has criticised the violence
Dinakaran was targeted after it published the results of an opinion poll headlined "What people think?"
The survey showed 70% of the respondents wanted Mr Stalin to succeed his father.
Only 2% of the respondents supported his elder brother, Mr Azhagiri.
Mr Karunanidhi, who has been grooming his younger son as his successor, has criticised the violence.
Tamil Nadu-based journalist Mayank Shukla told the BBC Hindi service: "It's a fight for succession."
He said Mr Azhagiri had high ratings in the southern part of the state, while his younger brother enjoyed popular support in the rest of Tamil Nadu.
Mob violence is not uncommon in Tamil Nadu and recently a court sentenced three members of a regional political party to death for killing three female students in 2000.
The girls died when a mob - allegedly comprising party workers from the AIADMK, the DMK's regional rival - set fire to a bus after their leader J Jayalalitha was jailed for corruption.
Jayalalitha maintains the violence was organised to discredit her party.