"This is a step to rid the state of insurgents and law-abiding citizens are urged to remain calm," army spokesman Lazarus Eli told Anadolu Agency on Friday.
"Every step is being taken to ensure the security of lives and properties across the state,” he said.
A military official said that the curfew was imposed following a night attack on a petrol station in Damaturu in Yorbe state on Thursday.
He said the gunmen exchanged fire with Nigerian security troops for hours.
There were no official figures about casualties.
"It is feared that the insurgents have already infiltrated the state,” he said.
"The attack on the petrol station (an NNPC mega station) and another one said to have been launched against a police station where an unspecified number of people died point to the fact that insurgents may have entered the state again."
Citing a security agent, local newspaper The Punch said that scores were killed in the attack on the police station.
There is no official confirmation regarding the attacks.
The last reported attack in Yorbe was on a college in September, which left 40 students dead.
Boko Haram, hitherto a peaceful group against bad governance and corruption, has since the 2009 killing of its leader Yusuf metamorphosed into a full-blown terrorist organization.
It has killed thousands of innocent civilians and security agents deployed to curb its terrorist campaigns in the country's north.
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