He will be interrogated to extract information regarding the investigation, a UP ATS spokesman said.
Efforts are also on to get remand of his two accomplices - Altaf Bhai Qureshi and Javed - arrested in Mumbai, the said.
They were part of an espionage racket linked to the Pakistan High Commission in New Delhi.
Special CJM Azad Singh had yesterday sent Aftab to 14-day judicial custody.
In the application seeking his police remand, the ATS said that since the accused has admitted that he was a spy of the Pakistani intelligence outfit, his custodial interrogation was required.
Aftab is said to have received training from the ISI in Pakistan and was in touch with officials in the Pakistan High Commission and ATS is said to be in possession of strong evidence against him.