Seven people were burnt after a passenger bus was firebombed in Chandina upazila of Comilla early today, police said.

The incident took place near Bangladesh Jute Research Centre on the Dhaka-Chittagong highway after midnight during Shab-e-Barat.

Deputy Commissioner Hasanuzzaman Kollol formed a five-member inquiry body, headed by additional district magistrate Golam-ur Rahman, to investigate the incident, reports a local correspondent.

A group of unidentified assailants hurled petrol-bombs on the bus through the window, Rasul Ahmed Mizan, officer-in-charge of Chandina Police Station, told The Daily Star quoting witnesses.

"We found pieces of glass and other evidences to confirm that it was a petrol-bomb attack. However, we don't know yet who carried out the attack and with what motive," he added.

Three of the burn victims were moved to Dhaka Medical College Hospital for better treatment. They were Anjan Kumar, 50, and Ranbir Sharma, 60, and Suman Chandra Nath, 31.

Shamanta Lal Sen, a doctor at the burn unit of DMCH, said Anjan suffered 23pc burns while Ranbir was more serious with 44pc burns. "They suffered burn on the chest and neck."

Later in the day, Suman was moved to DMCH with 15pc burns.

Khokan Chandra Sharma, 32, from Rangamati, and Emran Hossain, 25, from Gopalganj, were attending treatments at Comilla Medical College Hospital. Two others, Zahirul Islam, 44, and his wife Lovely Akhter, 27, attended primary treatments.

OC Rasul Ahmed could not say anything about the motive of the petrol bomb attack but added that procedures were underway to file a lawsuit in this connection.