Tahseen Akhtar, allegedly a member of Indian Mujahideen (IM), is the brain behind the string of explosions in Patna Sunday that left six dead, authorities said Monday.

"Tahseen Akhtar alias Monu, accused of several terrorist attacks, is man behind serial blasts in Patna," an Intelligence Bureau (IB) official here said.

"Initial investigation suggested the involvement of IM in serial blasts in Patna. The modus operandi and low-intensity bomb blasts are part of IM operation," the IB official told IANS declining to be named.

The IB official said that one of the suspects who was arrested has confessed to the involvement of IM in Sunday's seven blasts -- six of which took place in and around the Gandhi Maidan where Bharatiya Janata Party's prime ministerial candidate Narendra Modi later addressed a rally.

"More information will come out after likely arrest of three or four suspects involved in the blasts," the IB official said.

Tahseen Akhtar, considered to be close to Yasin Bhatkal, the man who co-founded Indian Mujahideen, hails from a village in Samastipur, about 100 km from Patna.

In the last few months, the National Investigation Agency (NIA) on more than 10 occasions raided his native village but failed to find him.

Earlier, the NIA issued an arrest warrant against Tahseen Akhtar, and also announced a reward of Rs.10 lakh for information that could lead to his arrest.

The NIA team arrested Mohammad Danish Ansari, an alleged operative of Indian Mujahideen, from Chakjora village in Darbhanga in January 2013. Ansari is allegedly also a close associate of Yasin Bhatkal.

Security agencies claim Ansari provided shelter to Yasin Bhatkal in 2009-10 in Bihar.