A gang hurled petrol bombs at two post offices in Mylapore and Mandaveli just past midnight of Monday, setting off a fire and tension in the locality. No one was injured.

Police on Tuesday arrested four persons on charges of being involved in the incident. They are investigating the CCTV footage from a nearby building in Mylapore to ascertain if more people are involved.

Joint Commissioner of Police (East) K. Shankar said the detained men are cadre of the Dravidar Viduthalai Kazhagam, a Tamil nationalist group.

“The CCTV installed at a building near the Mylapore post office captured the attack.”

Police said the motive of the attack is to send a message against Indian government’s participation in the Commonwealth Heads of Government Meeting (CHOGM) to be held in Sri Lanka in November.

Officials at the Mylapore post office on Kutchery Road located close to the Mylapore police station said two guards including an armed person deployed on the premises heard something unusual and spotted smoke coming from the Business Post Centre in the basement. “They noticed some men walking out of the gate that always remains open as there are residential quarters near the post office building,” an official at the post office said.

“Fire spread through the basement and the men tried in vain to put it out. It could be extinguished only by the Fire Department.”

The gang members who had come on two motorcycles hurled four petrol bombs at Mylapore post office, of which one did not explode.

The group then proceeded to Mandaveli post office on R.K. Mutt Road shortly and launched a similar attack, causing minor damage.

At the Mylapore post office, an electronic franking machine used to make stamp impressions for postal envelopes and a split AC unit were charred. Thousands of letters were damaged. Police identified the arrested as Umapathy, Ravanan, Marimuthu and Manoharan.

Charges under Sections 285 (negligent conduct with respect to fire or combustible matter), 427 (mischief causing damage), Explosive Substances Act and Tamil Nadu Public Property (prevention of destruction and loss) Act were pressed.

They were remanded in judicial custody and sent to Puzhal prison.