Banned terror outfit Indian Mujahideen (IM), responsible for bombings in different parts of the country, could be behind Wednesday's Bangalore blast, government sources said.
They said as per initial reports Improvised Explosive Devices (IED) was planted near the office of ruling BJP office in the southern part of the city and the blast material Ammonuium Nitrate had been frequently used by IM in the past.
"It is too early to point a finger at any group but the needle of suspicion goes to IM," sources said.
The blast took place just on the eve of third anniversary of blast in Bangalore's Chinnaswamy Stadium, which too is suspected to have been carried out by IM.
Sources said the bombing was indeed a "terror attack" and the city was lucky that it avoided a major tragedy since till yesterday there was a huge crowd at the site as BJP poll tickets were distributed till last evening.
Besides, in the nearby temple, there were many devotees yesterday being the Tuesday, considered to be auspicious especially during ongoing 'Navaratra' period.
"Since the BJP ticket distribution is over and today being Wednesday, there is less crowd in the place, thus avoiding a major tragedy. But we are sure that the spot was chosen carefully," a source said.
The Home Ministry has already sent a team of NIA and a bomb disposal squad of NSG had been sent to Bangalore to help the local police in post-blast investigation.
Karnataka government has not sought additional central forces as adequate personnel have been sent to the state in view of the forthcoming assembly elections.
Meanwhile, Home Minister Sushilkumar Shinde is likely to travel to Bangalore tomorrow to visit the site as well meet those who were injured.
The state BJP said the police had confirmed the blast occurred from the bike, which had Tamil Nadu registration. They said it had happened when party state president, chief minister and national leaders could have been present.
Police said Karnataka State Reserve Police personnel on security duty were injured as they rushed out of their van parked nearby on seeing the vehicles going up in flames.
Two of the injured were college students returning home after tuition.
"Our van was fully damaged, the glass panes shattered, with splinters hitting us. The impact of the blast was so much that the van seats sprung up, I almost hit the roof. I cannot hear from my left ear now," 50-year-old Meerannavar, an injured policeman, said at hospital.
58-year-old Kunjappa, a KSRP Sub-Inspector, said "the sound was such, I felt my head would split into two. While I saw flames rising from the two vehicles, the bike was in pieces."
Kunjappa's hearing has been impaired and he has suffered injuries all over his body.
The terror act has triggered a war of words between the Congress and BJP.
"If the blast near BJP's office in Bangalore is a terror attack, it will certainly help the BJP politically on the eve of election," Congress leader Shakeel Ahmed commented on microblogging site Twitter. Embarrassed, his party, however, dissociated itself from the remark.
In New Delhi, BJP President Rajnath Singh said the "terror act" appeared to be the job of some sleeper cells active due to "lack of efforts" in fighting terror by the Centre.
Singh refused to react to Ahmed's contention that the blast would help BJP, saying "I don't believe this has been stage-managed by somebody. Acts of terror are taking place across the country."
Blast gutted cars, shook buildings, says eyewitness
An eyewitness of the Bangalore blast, Ravi Chandaran said the sound created by blasts that occurred this morning made him nearly faint.
A shell-shocked Ravi Chandaran said, "We heard a loud sound. For a few minutes, I could not even register what had happened. When I could actually see, there was fire everywhere. Three cars, three bikes and a police van were on fire."
He added: "Three cars were gutted and four persons were injured. There was fire everywhere."
According to reports, four people were injured in the explosion, which took place outside the Bharatiya Janata Party (BJP) office in Bangalore on Wednesday.
A number of vehicles, including three cars, three bikes and a police van, were destroyed in the fire.
Emergency services rushed to the spot to douse the fire and police cordoned off area.
Investigators are looking into the cause of the blast.
Earlier, a team of forensic experts was combing the area for any evidence to ascertain the cause of the explosion.
At the time of the explosion, BJP workers had gathered at the party office in large numbers , as today was the final day to file nominations for the upcoming assembly elections in the state.
Wednesday's explosion is fourth terror attack in Bangalore
The blast near the BJP office in Bangalore Wednesday is the fourth terror strike in the Karnataka capital, home to renowned educational institutions and global information technology firms.
The blast, which left 16 people injured -- two seriously, took place exactly three years after the twin explosions at Chinnaswamy Stadium in the city centre, ahead of an Indian Premier League T20 cricket match, which left 15 injured.
The first terror attack in Bangalore was at the famous Indian Institute of Science (IISc) on the evening of Dec 28, 2005, when delegates coming out of an international conference were fired on, leading to the death of M.C. Puri, a retired professor of the Indian Institute of Technology-Delhi. Four people were injured in that attack.
The IISc is about five km from Wednesday's blast site in Malleshwaram, a residential locality in north Bangalore.
Six people, suspected to be members of terror outfit Lashkar-e-Taiba, have been sentenced to life imprisonment by a Bangalore court for the 2005 attack.
In the second terror attack in the city on July 25, 2008, one person was killed and six people were injured when a series of bombs fitted with timer devices went off in a span of 45 minutes in central, east and west Bangalore.
Around 30 people are facing trial for this attack.
The most prominent among them is Kerala-based People's Democratic Party (PDP) chief Abdul Nasir Maudany, who has been in a Bangalore jail for several months now.
The third terror strike was at Chinnaswamy Stadium, where two low-intensity bombs went off, about an hour before the start of the Royal Challengers Bangalore-Mumbai Indians match of April 17, 2010, injuring 15 people and delaying the match by an hour.
The explosions damaged the boundary wall of the stadium.
The next day, an explosive device was found near Gate No.1, generally used by the players and VIPs to enter and exit the stadium.
So far, seven people have been arrested in the Chinnaswamy Stadium blasts, including Fasih Mohammed, who was detained in Saudi Arabia, and recently deported.