Hundreds of civilians are fleeing Nigeria’s northeastern city of Maiduguri as fears grow that Boko Haram militants may try to attack the Borno state capital after seizing towns and territory around it, residents said on Thursday.

Heavily-armed Boko Haram fighters using captured military vehicles and weapons have taken towns and villages to the north, east and south of Maiduguri in the last few weeks and days in an apparent strategy to encircle the city and hold territory.

Apprehension among Maiduguri residents grew after fierce fighting since Monday between Nigeria’s military and attacking Boko Haram fighters over the town of Bama, 70 km (45 miles) southeast of Maiduguri. Thousands have fled Bama amid conflicting reports of who has control.

The militants, who have issued videos of themselves storming into towns with guns blazing aboard trucks mounted with heavy machine guns, also took the smaller town of Bara on Tuesday, to the southwest of Maiduguri.

Boko Haram internally displaced people in Adamawa state

Boko Haram, whose leader Abubakar Shekau last month declared a “Muslim territory” in the northeast after capturing the town of Gwoza on the Cameroon border, is believed to be trying to mimic the example of the Islamic State (IS) in Syria and Iraq which announced the creation of a separate caliphate there.

“They are creating territory for themselves … they have seen what IS have done, so they are trying to imitate them,” Musa Sumail, a human rights activist in Maiduguri who reports on the violence in the northeast, told Reuters.

The Borno state government and the armed forces have said Bama remains under government control, but did not immediately respond to calls asking for updates on the security situation.

Travelers packed bus stations in Maiduguri seeking transport westwards towards Damaturu in neighbouring Yobe state, the only safe exit route out. Vehicles laden with passengers and possessions were also seen on the Maiduguri-Damaturu road.

“I’m leaving now because people keep saying Boko Haram may attack Maiduguri anytime and it is possible,” said Saka Lawal, a car mechanic who was leaving with his wife and two children.

Civil servants, traders and even the families of soldiers were among those moving out, residents said.

President Goodluck Jonathan’s government and the armed forces have faced mounting public criticism of their apparent inability to check Boko Haram’s five-year insurgency, which has ravaged the poor northeast corner of Africa’s biggest economy.

.Reported by Reuters