Indian Home Minister P Chidambaram says it is likely an attack on the high court in Delhi on Wednesday was carried out by militants based in India.
At least 13 people were killed and 76 others were wounded.
Mr Chidambaram says the hallmark of the attack resembled that of a home-grown group.
''There have been three major attacks in India recently - in Pune, Mumbai and Delhi,'' he said.
In the past, India often blamed Pakistan-based groups for carrying out attacks on Indian soil.
''That threat remains - but we must also look at Indian modules or India-based modules which are capable of carrying out terror attacks,'' said Mr Chidambaram.
The BBC reports the government is under increasing pressure following the latest attack.
There are concerns that its security and intelligence agencies are still not in a position to handle the growing threat despite pledges to do so following the attacks on Mumbai in 2008.
