The suicide attacker who had attempted to assassinate Afghanistan's spy chief had detonated a bomb hidden his underpants, according to the National Directorate of Security.

Friday's revelation comes a day after varying reports about the attempt on Asadullah Khalid's life. Previous reports had said the attacker, posing as a Taliban negotiator, threw a grenade into the NDS guest house Khalid was in at the time of the attack.

A statement released by the NDS read:

The organisers of this suicide attack ... skilfully placed the explosives in the underpants and around the genitals of  the suicide attacker ... [this] runs against all Islamic and Afghan principles. 

If confirmed, attempt on Khalid's life would mark the first instance of a suicide bomber carrying explosives in his underpants.

Khalid was moved to a US-run military hospital near the Afghan capital, where he is currently in stable condition.

"We can confirm that he has been moved to the hospital at Bagram," a spokesman for the International Security Assistance Force told the AFP news agency.