Designation will mean tougher sanctions under the terrorism prevention act for suspected bandit gunmen, their informants and supporters, such as those caught supplying them with fuel and food.
Nigeria has labelled criminal bandit gangs blamed for mass kidnappings as "terrorist groups" in an attempt to deter violence in the country's northwest.
In the official gazette on Wednesday, the federal government labelled activities of Yan Bindiga and Yan Ta'adda –– references in the Hausa language to bandit gunmen –– "as acts of terrorism and illegality".
"I think the only language they understand –– we have discussed it thoroughly with the law enforcement agencies; the security chiefs, the Inspector General of Police –– is to go after them," President Muhammadu Buhari told Channels Television, according to its website on Wednesday.
"We labelled them terrorists... we are going to deal with them as such."
The official gazette referred to criminal gangs who carry out mass kidnapping of school children, abduction for ransom, cattle rustling and destruction of property among other crimes.
The definition will mean tougher sanctions under the terrorism prevention act for suspected bandit gunmen, their informants and supporters such as those caught supplying them with fuel and food.
Nigerian daily newspapers often carry stories about bandit raids on villages and communities, where they steal cattle, kidnap families and terrorise residents.
Security forces have announced a crackdown, including air raids and a telecoms shutdown in parts of the country's northwest in an attempt to flush criminal gangs from their forest hideouts.
On Tuesday, police announced they had rescued nearly 100 kidnap victims in two raids on bandit camps in northwestern Zamfara state.
A decade-long battle
Heavily armed gangs have long plagued Nigeria's northwest and north-central states, raiding villages to loot and kidnap for ransom, but violence has become more widespread.
President Muhammadu Buhari's government, already battling a more than decade-long militants conflict in the northeast, had been under pressure to do more to halt attacks from the criminal gangs.
Last year, bandit gangs made international headlines with a serious of high-profile attacks of schools and colleges to kidnap scores of pupils for ransom. Some of those students are still being held.
Nigeria's bandit violence has its roots in clashes between nomadic cattle herders and sedentary farmers over land and resources. But tit-for-tat attacks have over the years spiralled into broader criminality.