This brings the total number of suspects involved in the planning to three.
Saleh said Monday one of the three, Ahmad, was killed in a clash with security forces in Paktia province and another was arrested.
The first arrest of a suspect – Adel – was made last week.
“A third member of the cell has been arrested and will be transferred to Kabul in the next few hours.
“The case is being developed rapidly. We will keep you informed,” Saleh said.
According to Adel’s confession, members of the cell had staked out the university ten days before the attack.
They realized that people who were well dressed would not raise suspicions at the entrance gate.
With this plan in action the attackers were able to enter the university one after the other wearing fashionable clothes, with fashionable students, and their bags were not searched, Saleh said.
“They [attackers] decided that if the first one was arrested, the second one would have to shoot the police with a rifle on the spot,” Saleh added.
Saleh added that the suicide bombers have now been identified and their names would be revealed to the Afghan people in a day or two. “The families of the suicide bombers are under the supervision of the NDS,” Saleh added.
Speaking at a 6:30 am session with other officials, Saleh said that the mastermind of the attack on Kabul University, whose name is “Adel”, from Panjshir province, was a student at the Kabul Faculty of Sharia three years ago.
In the attack on Kabul University at least 30 were killed and more than 30 others were wounded.
ISIS (Daesh) claimed responsibility for the siege, which lasted six hours and although the Taliban immediately distanced themselves from the attack, many critics have dismissed Daesh’s claims and blame the Taliban.