There are striking similarities between Sunday night's blast outside a restaurant in Bengaluru's central business district and explosions on a train in Chennai in May and in Pune in July, sources said on Monday.
Sources in Bengaluru Police, which will be assisted by a National Investigation Agency team in its investigation, said the most obvious common thread between the three blasts is the usage of ammonium nitrate based IEDs which were packed with shrapnel.
A senior investigating officer told Hindustan Times there are many other similarities between the three blasts but those details cannot be released in the public domain yet.
Additional commissioner of police Alok Kumar said two investigating teams have been despatched to Pune and Chennai for further probe the terror link.Intelligence sources told HT two terror alerts were issued to the Bengaluru Police in the last two days.
Responding to claims that quality of the CCTV footage from establishments near the blast site is extremely poor, Kumar said investigators are analysing material from the cameras which have recorded the incident from multiple angles.
Earlier, briefing the media after chairing a high-level meeting attended by state home minister KJ George, DGP L Pachau, police commissioner MN Reddi and security experts, chief minister Siddaramaiah said two broad angles are being probed.
The CM said there is a possibility the blast was triggered by the same extremists who threatened to avenge the arrest of pro-ISIS Twitter handler Mehdi Biswas.
The second angle being probed is based on intelligence inputs that the five terror suspects who escaped from the Khandwa jail in Madhya Pradesh in October 2013 could be involved in the blast, he added.
Siddaramaiah said the state had received inputs that the five men had slipped into Karnataka
Home minister George said "...We have to see what is the cause who is behind it".
In Delhi, minister of state for home Kiren Rijiju said it was a "terror attack" possibly carried out by banned extremist outfit SIMI.
"Definitely, it is a terror attack," Kiren Rijiju told the media when asked about the blast.According to Bengaluru Police commissioner Reddi, no group has claimed responsibility for the low intensity blast.
The "low intensity IED blast" which occurred between 8:30 and 9pm on Church Street, 50 meters from the Hindustan Times office, on a footpath outside the popular Coconut Grove restaurant.
The IED placed in a plant in front of the restaurant went off on Sunday night killing Bhavani Devi, a resident of Mount Road in Chennai, and injuring her relative Karthik.
Thirty eight-year-old Devi had come to Bengaluru four days ago to celebrate Christmas with her family and was with her two daughters and eight other family members when the blast occurred.
Dr Kanchan Sanyal, who was treating Devi at Mallya Hospital, confirmed to the media that she died of shrapnel wounds to her head.
Sanyal said despite CPR Devi, who had an open wound, could not be revived as her brain tissue was exposed.
According to officials, the group was crossing the road and heading towards Coconut Grove. The device went off just before Devi got to the restaurant.
Two other persons who also sustained injuries were identified as Vinay and Sandeep and are undergoing treatment at HOSMAT Hospital.
The restaurant is close to the fashionable Brigade Road and MG Road, dotted with bars and restaurants with teeming crowd on weekends.
(With PTI inputs)