Security stepped up in Delhi
A senior police official said personnel have been "alerted" and there is extra vigil across the city.
"There is an emphasis on checking the vehicles which are leaving and entering the city. We have deployed personnel across the city. There is nothing to panic," the official said.
Police have also stepped up vigil at railway stations, ISBTs, airport, Metro stations, markets and other crowded places in the capital.
16 people, including eight policemen, were injured in the blast near the BJP city office in Bangalore.