The Nigerian military has been targeting multiple sites across the country's northeast to rid the area of Islamist insurgents. President Goodluck Jonathan declared a state of emergency in the region on Tuesday.
Camps housing Boko Haram and other Islamist insurgents came under siege from Nigeria's air force on Friday, according to a military spokesperson.
"A number of insurgents have been killed," Brigadier General Chris Olukolade said.
The military reportedly focused much of the fighting on Borno where insurgents have taken control over many towns.
Insurgent training camps in the Sambisa Game Reserve in Borno State came under heavy fire, but Olukolade said that the air force had also attacked numerous other sites.
"It is not just Sambisa, every camp is under attack. But we have not done the mopping up operations on the ground to determine the numbers killed," he said.
He declined to confirm the number of troops deployed to the region, estimated by local reports to be several thousand.
The government's decision to declare a state of emergency on the states of Borno, Yobe and Adamawa has drawn mixed responses.
A resident from the Borno town of Krenuwa told the news agency AFP he had fled after President Goodluck Jonathan ordered the military operation because the announcement had caused an upsurge in militant activity.
"I was so scared for my life and my family's which led me to decide to leave," Abur Kullima told AFP.
Another Borno resident told news agency DPA that communities expected the government to resort to more peaceful means first.
"We had expected the emergency as the last resort to this whole crisis," the resident from Maidugiri told DPA. "The military should this time assert their control and the confidence of the people will be restored to provide information safely."
Boko Haram - whose name means "Western education is sacrilege" -emerged in Nigeria in 2009. The insurgent force has been for Shariah, or Islamic law, to be imposed across the country of 170 million, of which about 40 percent is Christian.
Since 2010, Boko Haram has carried out dozens of attacks, killing at least 1,600 people.
kms/dr (AFP, Reuters, dpa)