LAGOS - Nigeria's military imposed a 24-hour curfew in parts of a northeastern city on Saturday as it pressed on with a campaign against Boko Haram Islamists that have sent residents fleeing the region.
Locals in a remote insurgent stronghold near the border with Cameroon have begun fleeing their homes after military fighter jets and helicopters carried out air strikes on Islamist camps.
Nigeria launched the sweeping operation against Boko Haram this week, deploying several thousand troops across three states where President Goodluck Jonathan declared a state of emergency after the Islamists seized territory and chased out the government.
The group, which has said it is fighting to create an Islamic Nigeria's mainly Muslim north, has carried out scores of attacks in recent years, and has become emboldened and better armed in recent months.
The military said dozens of insurgents have been killed in the offensive targeting all three states put under emergency decree, including Adamawa and Yobe, but Boko Haram's traditional base of Borno is expected to see the most bloodshed.
Borno state military spokesman Lieutenant Colonel Sagir Musa in a statement listed 12 neighbourhoods in the city of Maiduguri where a "24-hour curfew" was being imposed.
In a separate release, the military said it had arrested 65 suspected Boko Haram members who were trying to enter Maiduguri after fleeing aerial bombardments elsewhere.
In the Marte district of Borno, some residents were fleeing east towards a town on the Cameroon border, 42 kilometres away.
"It has been scary in the past three days," said Buba Yawuri, whose home is in the town of Kwalaram in Marte but who has fled to the border town Gomboru Ngala.
"Fighter jets and helicopters kept hovering in the sky and we kept hearing huge explosions from afar," he told reporters.
He said that as the air assaults began, the security forces told all residents to stay indoors, cutting off his family's access to food and water.
"I couldn't hold on any longer. I took the bush path" and reached Gomboru Ngala early on Saturday, he said.
Shafi'u Breima, a resident of Gomboru Ngala, told AFP that the border town is receiving a continuous flow of people arriving from Marte and neighbouring areas.
The phone network in Borno state has all but collapsed since the emergency measures were imposed but residents in Gomboru Ngala use phone services from Cameroon and have been sporadically reachable.
The remote, thinly populated region has porous borders where criminal groups and weapons have flowed freely for years.
The military has sealed previously unguarded crossings to block Boko Haram fighters from fleeing during the offensive.
The military campaign could prove to be the biggest ever against Boko Haram and is believed to be the first time Nigeria has carried out air strikes within its own territory in more than 25 years.
Aerial support was believed to have been used against rioters in the north in the early 1980s.
Many have warned that there is a risk of high civilian deaths and Nigeria's military has been accused of massive rights violations in the past, including indiscriminate attacks on civilians.
US Secretary of State John Kerry said on Friday that he was "deeply concerned about the fighting in northeastern Nigeria" and urged the security forces to "apply disciplined use of force in all operations."
There are also doubts as to whether the insurgency can be crushed by force, amid concern that the militants will scatter and re-emerge when the offensive eases.
Nigeria has been urged by various camps to tackle the root social causes of the conflict, including acute poverty and excessive government corruption which has helped radicalise many young Muslims in the north.
The conflict is estimated to have cost 3,600 lives since 2009, including killings by the security forces.