Three people have been held in Chennai for their alleged involvement in the bomb blast near the Karnataka BJP office in Bangalore.
Two were arrested from Chennai and one from Madurai. They facilitated the attack and main culprits are still at large.
According to top police sources, Karnataka Police were assisted by their Tamil Nadu counterparts in a late night operation, in which two persons - Peer Mohideen and Basheer hailing from Tirunelveli were arrested from a lodge in Chennai.
The third person was arrested from Madurai, they said, adding the trio facilitated the blast while the main culprits were still at large.
Four men were recently detained in Kerala for their alleged involvement in the case.
The arrested are being taken to Bangalore for further investigation, sources said.
The Indian Express quoted senior officials close to the investigation saying that the blast involved a group not linked in recent times to terrorist activities in south India.
"We want to be sure about the group affiliations of the people involved before announcing the results of the investigations. We had very strong leads and that took us to the perpetrators," the daily cited a senior police officer.
The crucial leads in the investigation were the chassis number and engine number of the motorcycle that was used to plant the explosive device and a set of fake identities used to purchase SIM cards by people involved in transactions to buy the 1995 model motorcycle, it said.
The Express said that the officials also pointed to similarities of the Bangalore blast to those in Mumbai in July 2011, Pune in August 2012 and Hyderabad in February this year.
"There were many similarities between the recent blast and others in the past. One is that the trigger switches for the IEDs are placed with the explosives which leads to its destruction. The use of second-hand vehicles to plant the bombs is also a common thread," the daily quoted sources as saying.
A bomb placed on a parked motorcycle exploded near the BJP’s office in the Karnataka capital on April 17, injuring 16 persons.
The Malleshwaram area in north Bangalore was teeming with activity when the bomb went off at 10.30am as there is a temple nearby and it was also the last date for filing of nominations for the May 6 assembly elections.
The Union home ministry as well as state deputy chief minister R Ashok called it a “clear act of terror” and Union home minister Sushilkumar Shinde ordered an inquiry.
(With PTI inputs)