Nigeria's military has announced a "massive" deployment of troops to its restive northeast to tackle armed group Boko Haram, after the president declared a state of emergency in the areas.
President Goodluck Jonathan imposed a state of emergency in three states, including Yobe and Adamawa, but the offensive is widely expected to be concentrated in Borno, whose capital, Maiduguri, is a home base of Boko Haram.
"Nigerian Armed Forces... have commenced operations to rid the nation's border territories of terrorist bases," a military statement said.
Nigerian Armed Forces... have commenced operations to rid the nation's border territories of terrorist bases
"The operations which will involve massive deployment of men and resources, is aimed at asserting the nation's territorial integrity," it added.
Boko Haram has been fighting to create an Islamic state in Nigeria's mainly Muslim north since 2009. Hundreds of people have died in the conflict.
The group has recently stepped up attacks on government installations and security forces and is understood to control substantial territory around Lake Chad, where local officials have fled.
Reuters news agency reported shops and schools were mostly shut and there were few people on the streets as troops made their way into the cities.
"What I saw this morning scared me," said one man in Maiduguri, Ahmed Mari. "I have never seen soldiers on the move quite like this before."
Another man, Kabir Laoye, voiced widespread fears that civilians could be caught up in the conflict. "There is a lot of apprehension about the state of emergency," he said.
In his statement on Tuesday, Jonathan said troops would "immediately" be deployed to the areas.
He made a similar move in January 2012 following a spate of Boko Haram attacks, but in that case the decree only applied to specific local government areas in four states.
Al Jazeera's Yvonne Ndege, reporting from Nigeria, said the president's declaration was being made "to restore public safety and security".
"This move does to some extent fly in the face of much of the rhetoric we have been hearing about the government's efforts to broker a peace deal with Boko Haram," our correspondent said.
"They have been saying in the last few weeks that things are going well, that many Boko Haram fighters have surrendered, but clearly this decision to declare a state of emergency in these states and to send more troops there does seem to bring the success that the government have been talking about in to question."
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Officials say fighters control at least 10 local government districts of Borno state and are using porous borders with Cameroon, Chad and Niger to smuggle in arms and mount attacks.
Dozens of Boko Haram fighters in buses and trucks mounted with machine guns laid siege to the Borno town of Bama last week, freeing over 100 men from prison and leaving 55 people dead, mostly police and other security personnel.
Two weeks earlier, scores were killed in the fishing village of Baga, on the shores of Lake Chad, when troops from Nigeria, Niger and Chad raided it looking for fighters who had killed a soldier.
Local residents said soldiers were responsible for many civilian deaths.
Source: Al Jazeera and agencies