A cash reward has also been announced for those who come up with information which could help the police nab the assailants of a constable, who died in the attack.
An unpopular group which has links with LeT and SIMI has claimed responsibility for the attack and has warned of similar attacks if the perpetrators of the 2007 Mecca Masjid firing are not arrested.
Sketches of the assailants are being drawn based on the statements of a policeman and other witnesses who were present at the time of the incident.
"We have picked up 15 persons for questioning after gathering information from the shop-owners of the area who were eyewitnesses to the incident," a senior police officer said on a news agency report.
According to Police commissioner AK Khan, a Special Investigation Team (SIT), comprising of various investigating agencies for speedy probe into the incident has already started its work based on the information gathered from eye-witnesses and evidence.
Another police officer said "we are preparing the sketches of suspects on the information provided by Shanta Rao and other eye-witnesses."
Police has sought the help of the public to come up with information on the assailants which could help in the investigation and has announced a cash reward for any informer.
"Any person who provides information that leads to detection and apprehension of the accused responsible for this act (killing of Ramesh), will be rewarded with Rs 5 lakh by the police department," a statement from Hyderabad city police said late on Saturday, May 15.
On May 14, three motorcycle bound gunmen shot around three rounds on U Ramesh (26), who was posted in Shah-Ali Banda area in the communally sensitive Old City area in Hyderabad. Ramesh died on the spot.
Police suspect the role of alleged ISI operative Viqaruddin, also a member of the banned SIMI, behind the attack on the Ramesh.
Police said Viqaruddin has been involved in the two attacks on policemen in 2008 and 2009.