Prime Minister Manmohan Singh on Thursday spoke to Tripura Chief Minister Manik Sarkar to condemn the bombings in this state capital, which woke up to a sombre Eid morning after more than 100 people were injured in a series of four explosions the evening before.
Police have detained six people for interrogation.
"The Tripura chief minister apprised the prime minister about Wednesday's incident in the capital city," a senior official said.
Manmohan Singh, who had phoned Sarkar to inquire about the incident, expressed his sorrow and condemned the attack on innocent people, the official added.
Vice President Hamid Ansari also denounced the blasts and said "such mindless acts of violence coinciding with the festive season are aimed at disturbing peace and harmony", the official said.
Many markets in the state capital were closed after the serial blasts on Wednesday night that came on the eve of Eid-ul-Fitr and ahead of the five-day Durga Puja festival beginning on Sunday.
Disclosing that six people had been detained, Director General of Police Pranay Sahaya said: "Senior police officials are out on the streets to unearth the design behind the bombings."
"Contrary to media reports, nobody died in the blasts, although the condition of eight of the injured is critical."
Police had on Wednesday said two people were killed in the four explosions in crowded marketplaces within about an hour.
"We are yet to ascertain the nature of the blasts and the group behind them," the police chief said. "A red alert has been sounded all over the bordering state and the security forces have been asked to maintain a close vigil over the prevailing situation," he told reporters.
Three National Security Guard (NSG) experts from New Delhi and a team of experts from the National Forensic Laboratory in Kolkata are arriving to investigate the terror attack.
Tripura Chief Secretary Sashi Prakash is in constant touch with union Home Secretary Madhukar Gupta to finalise the strategies to deal with the prevailing situation.
Panic spread in Agartala - the capital city of Tripura which is surrounded by Bangladesh on three sides -- as two live bombs were recovered and defused in the heart of the city late on Wednesday.
No group has as yet claimed responsibility for the blasts.
Tripura, which has witnessed spells of insurgency and violence, had never been targeted with explosions.
The two banned separatists' outfits, All Tripura Tiger Force (ATTF) and the National Liberation Front of Tripura (NLFT), have been relatively quiet in recent years.
Police said the motive behind the blasts could be to create tension in the mixed population capital city on the eve of Eid-ul-Fitr and the approaching Hindu festivals of Durga Puja and Dussehra.