At least 16 people, including eight policemen and eight civilians, were injured in a blast that occurred 100 metres away from the BJP's office in Bangalore on Wednesday.
Five cars that were parked near the BJP's office in Malleswaram were gutted in the blast. A police van was also damaged, according to officials.
Initial reports suggested a cylinder explosion, but police later said that the explosive was placed on a motorcycle. They recovered 500 grams of explosives from the blast site.
Karnataka Home Minister R Ashok called the incident a terror attack and said that improvised explosive Device (IED) was used in the explosion. He appealed for calm and assured that the offenders will be caught.
Police suspect that it could be "foul play", as today is the last date for filing nominations of candidates for the Karnataka polls to be held on 5 May.
The area has been cordoned off. Forensic teams have been sent to the location to dig out any clues. A National Investigating Agency (NIA) team is expected to arrive at the scene soon.
The incident happened close on the heels of the twin-bomb blasts at the Boston Marathon event in the US on Monday. Three people, including an eight-year-old boy, were killed in the blasts. More than 100 were injured.