The blast occurred around 8.30 pm near Coconut Grove, a famous restaurant on Church Street, close to the fashionable Brigade Road, which is dotted with bars and restaurants with teeming crowd on weekends.
A man and a woman were hit by the shrapnels and have been admitted to a nearby hospital, City Police Commissioner M N Reddi told reporters at the site, as police cordoned off the area.
The woman identified as Bhavani was in a serious condition and the other person was out of danger, he said.
Union Home Minister Rajnath Singh called up Karnataka Chief Minister S Siddaramaiah and assured him that all help will be given by the Centre.
Singh said the Chief Minister apprised him of the situation.
“Spoke to Karnataka CM Shri S Siddaramaiah regarding the Bangalore blast. He apprised me of the situation. Centre ready to provide all help," Singh tweeted.
"At about 8:30 pm on the Church street outside the restaurant called Coconut Grove there was an explosion heard.. we have found that there was improvised explosive device that was used by some culprits and in this explosion two persons have been injured," Reddi said.
"As far as the current information is concerned the IED that has been used is like a low intensity bomb and some shrapnels have obviously hit the individuals who have been injured. This is the information we have," he said.
Reddi said the entire city police force had been mobilised and added that additional force from Karnataka State reserve police had also been sought.
Internal security division experts along with the forensic team, dog squad as well as anti-sabotage check team have rushed to the spot.
As per information two unidentified men have been detained by the police. The detainment has been done after seeing a CCTV footage.