Now India's northeast region comes under terror attack, serial bomb blasts kill at least 5 in Agartala

Tripura's Director General of Police Pranay Sahay said initial investigations have revealed that Muslim militants from Bangladesh could be behind the bomb attacks. He, however, refused to identify any group.

Till now, no militant group has claimed responsibility for the attacks. Tripura's two major ethnic insurgent groups, the National Liberation Front of Tripura (NLFT) and the All Tripura Tiger Force (ATTF) have been lying low for the past few months and have, till now, been known to launch attacks only security forces and villages populated by Bengali settlers.

"Security along the border has been tightened," he said, referring to nearly 840 km of porous border with Bangladesh. Agartala is about 5 km from the international border.

Police investigators are trying to ascertain the nature of the bomb.

"We are trying to ascertain what kind of explosives had been used," said police spokesman Nepal Das, adding that the serial explosions were the first such attacks in Tripura.

Initial investigations have revealed that timers were used to make the bombs go off and the bombs had pellets inside to intensify the impact.