The Tripura police have arrested four persons, including three Bangladeshi nationals, in connection with the serial blasts in Agartala. Additional forces have also been deployed throughout the state.

According to a source, the four arrested persons were identified as Nurul Amin (43) from Gajaria and three illegal Bangladeshi nationals � Md Joinal (28) from Chittagong district in Bangladesh, Roshan Jamam from Sylhet and Abdul Malek (22) from Rangpur.

The three Bangladeshi nationals were arrested from Lankamura area of Agartala by the police late on Thursday night.

Serial blasts in Agartala; 2 killed

The source informed that cross border movements of criminals and terrorists, along the border with Bangladesh near Agartala, were possible due to gaps in the border fencing. The police estimate that there are over 25 camps of Tripura militant groups on Bangladesh soil.

The Criminal Investigation Department of the state police is investigating the serial blasts. A two-member team of the National Security Guards headed by one Major Karambhir and another team from the Central Forensic Science Laboratory from Kolkata are assisting the Tripura police with the probe in the serial blasts, which put the hilly state on the country's terror map.

"There are some similarities to earlier serial blasts. The initial chemical tests have confirmed the presence of ammonium nitrate and fuel oil (furnace oil or transformer oil) in explosive devices," Tripura Director General of Police Pranay Sahay said.

Additional personnel of Assam Rifles and Tripura State Rifles have been deployed in Agartala to beef up security. The DGP informed newsmen that close circuit televisions would be installed in vulnerable spots in the city during Durga Puja. The state police will also ask other blast-affected states to share their intelligence and technical expertise during the course of investigation.

The Opposition Congress has called for an inquiry by the Central Bureau of Investigation into the serial blasts, even as the state Pradesh Congress Committee president S R Burma accused the Left Front government of being complacent about security, despite warning from the Centre.