Afghanistan has arrested six men on charges of planning a bombing that killed five United Nations staffers, the national security chief said Saturday.

One of those in custody, Mullah Qari Aminullah, was a religious teacher at a Kabul mosque and concealed the three suicide bombers in his home, Sayed Ansari alleged. Aminullah was arrested Thursday in Medina, Saudi Arabia.

Ansari said the alleged bombers were from Pakistan.

The bombing at a guest house used by U.N. staff also wounded five people Wednesday. At a meeting Friday with U.N. employees in New York, Secretary-General Ban Ki-moon said two of the staffers who were killed were working on the Afghan elections and two were security personnel. The fifth had not been identified, he said.