Raipur, Aug 23 - A day after a little known group triggered a powerful blast right in front of state's ruling Bharatiya Janata Party (BJP) headquarters in the heart of the city, the police are yet to ascertain who was behind it.

The blast from a country-made bomb ripped through the front part of a passenger bus parked outside the BJP headquarters, Ekatm Parisar. It created scare though the bus belonging to Mahamaya Travels was empty at that time.

Police officials here said they were struggling to gather details about the Don Group that had claimed responsibility for the attack.

A slip was found in the bus which claimed that the blast was the handiwork of Don Group and it also warned of more such attacks 'if the rich people continued to try to grab land of the poor in Raipur'.

The group had also claimed to have exploded a bomb in Raipur's busy Budha Talab area in March this year.