NIA sources said Fakruddin and Ahmed were arrested from Mirzapur in eastern Uttar Pradesh for allegedly procurring material used in the blasts during the rally.
While five blasts were triggered within the rally venue, two exploded outside in which eight people, including a militant of Indian Mujahideen, were killed and over dozens injured.
The NIA, which was handed over the case, has been carrying out investigations into the case and with the help Intelligence Bureau, it had nabbed Yasin Bhatkal who had named the main culprits behind the incident.
The NIA arrested four people, including Mohammed Imtiyaz Ansari who was apprehended by the public when he, along with another IM accused, was assembling bombs inside a toilet at a makeshift railway station in Patna.