DHAKA, Aug 31: The August 17 serial bombing in Bangladesh was a combined attack of two Islamic extremist groups and an outlawed ultra-leftist party, said intelligence agencies investigating the unprecedented explosions.

They said Jagrata Muslim Janata, Jamaatul Mujahideen, and the Janajuddha faction of the outlawed Sarbahara Party coordinated and participated in the attack. The investigators did not, however, rule out a foreign hand behind the attacks.

They said that despite the feud between the Islamic outfits and a faction of the left radical Sarbahara Party, the three organisations buried their differences temporarily and cooperated with each other to intimidate the government into leaving them alone.