Sources in the NIA said the sketches -- the first to be released in the probe -- were made public on the basis of details provided by three eyewitnesses who apparently saw the suspect shortly before the blasts on July 7 and also material emanating from CCTV footage.
The two sketches, one in which the suspect is wearing a green mask and another bare face, were posted by the NIA on its website.
The sources said the suspect in monk attire was seen in the CCTV footage moving around Buddhism's holiest shrine in suspicious circumstances at around 3:30 AM to 4:30 AM shortly
before the blasts.
NIA also released the CCTV footage and sought information about the suspect.
Senior NIA officials said attempts made to locate this person have not yielded any result so far prompting the central probe agency to release the sketch.
NIA sources said the CCTV footage was being refined further to get a clearer image of the suspect.
Among the three eyewitnesses, whose names have been kept secret for probe purposes, two are foreigners and one local.
The foreigners are from Sri Lanka and Thailand while the third one is a local Gaya native, the sources said.
The services of the private security company within the temple premises, meanwhile, has been terminated after the Maha Bodhi Temple Management Committee took strong note of security lapses that resulted in the serial bomb blasts.
Ten bombs went off in and around Mahabodhi temple in Bodh Gaya on July 7 in near synchronised explosions in which two monks were wounded.
NIA had earlier detained two natives of Gaya from Maoist-infested Barachhati and four youngsters, including a girl, in Patna in connection with the incident.
But, they were all released for want of evidence.
The agency has already announced a reward of Rs 6 lakh for providing information about suspects in the blast.