The army said the group posed security challenge and had been metamorphosing from one stage to another.
In a statement in Abuja on Friday, Maj.-Gen. John Enenche, the Director, Defence Information (DDI), therefore, restated the commitment of the Armed Forces to confront "all security challenges facing the country."
Enenche also assured of the protection of lives and property in all parts of the country by the military.
He said that the IPOB posed security challenge and had been metamorphosing from one stage to another.
"After due professional analysis and recent developments, it has become expedient to notify the general public that the claim by IPOB actors that the organisation is non-violent is not true.
"Hence, the need to bring to public awareness the true and current state of IPOB.
"In this regard, some of their actions, clandestinely and actively, that have been terrorising the general public include:
"The formation of a Biafra Secret Service, claimed formation of Biafra National Guard, unauthorised blocking of public access roads and extortion of money from innocent civilians at illegal road blocks.
"Militant possession and use of weapons (stones, molotov cocktails, machetes and broken bottles, among others) on a military patrol on Sept. 10, 2017.
"Physical confrontation of troops by Nnamdi Kanu and other IPOB actors at a check point on Sept. 11, 2017 and also attempt to snatch their rifles.
"Attack by IPOB members on a military check point on Sept. 12, 2017, at Isialangwa, where one IPOB actor attempted to snatch a female soldier's rifle.
"From the foregoing, the Armed Forces of Nigeria wish to confirm to the general public that IPOB from all intent, plan and purpose as analysed, is a militant terrorist organisation," the DDI said.