Boko Haram crisis: Nigeria air raids target militants
The Nigerian military has launched air raids on militant training camps in the north-east of the country, officials say.
An army spokesman said jets and helicopter gunships had been used to attack several camps.
He told the BBC that a plane had been hit by anti-aircraft fire but had managed to return to base.
States of emergency were declared this week in three north-eastern states hit by Boko Haram's Islamist insurgency.
Nigerian military spokesman Brig Gen Chris Olukolade said two militant bases in the Sambisa Forest Reserve were destroyed in raids.
The reserve is about 70km (45 miles) south of the Borno state capital, Maiduguri, where the militants first emerged in 2009.
Reports say dozens of militants have been killed, but there has been no independent confirmation.
Nigerian forces are trying to regain control in the states of Adamawa, Yobe and Borno.
"It is not just Sambisa, every camp is under attack," the Reuters news agency quoted Brig Gen Olukolade as saying.
'Land and air'
Meanwhile, explosions and gunfire were heard overnight on Thursday in Katsina state, where gunmen launched several attacks.
Residents told the BBC's Hausa service that banks, police stations and prisons were destroyed in the town of Daura, near the border with Niger.
They said they had seen the bodies of five members of the security forces and three militants, but there has been no official confirmation of casualties.
Soyinka Okupe, a special assistant to Nigerian President Goodluck Jonathan, said that government forces would continue to hit the militants hard.
"Their mandate is to ensure that activities of Boko Haram insurgents and rebels in these areas are brought to zero level.
"So they will employ everything that is in their power to effect that, including land and air."
Mobile phone networks were not functioning in many parts of north-east Nigeria on Thursday.
A security official told the AP news agency that the mobile phone service had been shut down during the military operation.
Militants have previously attacked mobile phone masts in the area in an effort to disrupt communications.
Residents staying inside
Brig Gen Olukolade said the plane damaged by anti-aircraft fire on Friday had returned to base safely, while the "terrorist base" was subsequently "completely destroyed".
This is the first time Boko Haram has been reported to have used such heavy weaponry against aircraft.
A Maiduguri resident told the BBC that the city was unusually quiet on Friday, with most people staying inside.
Brig Gen Olukolade said "several thousand" troops had been sent to the three north-eastern states to tackle Boko Haram.
The three semi-desert states, which border Niger, Chad and Cameroon, are roughly the size of England or the US state of Illinois but have a population of just 10 million.
The BBC's Will Ross in Abuja says targeting Boko Haram's rural bases or training camps should pose no great challenge for the military; the hardest part of this campaign will be in urban areas like Maiduguri, where the militants are living among the civilian population.
The president said the army would take "all necessary action" to "put an end to the impunity of insurgents and terrorists", saying they had taken down the Nigerian flag and replaced it with a foreign emblem in some parts of the country.
Human rights organisations have criticised some of the Nigerian military's previous operations because of the resulting civilian casualties.
Boko Haram, whose name means "Western education is forbidden" in the local Hausa language, is fighting to overthrow the government and create an Islamic state in the north.
Although they often attack Christians and government targets, they have also killed many Muslim civilians.