The crude bombs, concealed near refugee camps and roadside stuffed with nuts and bolts, exploded during the busy lunch hour at Adugodi, Madivala, Nayandahalli, Pantharapalya and Vittal Mallya Road.

"In all the blasts, low intensity time devices were used. They want to cause damage to human lives. Explosives were used in quantity equal to one to two grenades," Bangalore Police Commissioner Shankar Bidri said.

While no one has claimed responsibility so far for the blasts, sources in the Union Home Ministry suspected Pakistan-based Lashker-e-Toiba along with the local support of SIMI to be behind the attacks.

Bangalore Police Commissioner Shankar Bidri termed it as an ‘act of miscreants’ trying to disturb peace in Bangalore.

"We are conducting investigation into the blasts. Bomb disposal squads and forensic experts have reached the spot. Bangalore Police is on high alert," Birdi said.

The serial blasts comes in less than two years after the attack at Indian Institute of Sciences in which an IIT professor M C Puri fell victim to terrorists.

In the national capital, Union Home Secretary Madhukar Gupta spoke to the state chief secretary and sought a detailed report about the incident.

On Vittal Mallya road, the explosion took place in a park. No one was injured in that blast, police said.