MAIDUGURI, Nigeria (AP) — Camps for tens of thousands of people displaced by Boko Haram will have to stay open beyond the end of this month as Nigeria's military continues to fight the extremists in so-called liberated areas, officials say.

The governor of the northern state of Borno, Kashim Shettima, told reporters on Tuesday that it is not yet safe to return people to their homes in many places across the region. The government's goal was to close all of the camps by the end of May. The humanitarian crisis is considered one of the worst in the world.

Nigerian President Muhammadu Buhari late last year declared Boko Haram "crushed," but the military now says operations continue to clear the extremists from their strongholds.

"What we are doing now is mop-up of the fleeing Boko Haram terrorists who are running into the fringes of the forest as well as border areas," said Maj. Gen. Lucky Irabor, who commands the counterinsurgency operation in the northeast.

Boko Haram continues to carry out suicide bombings in the Borno capital, Maiduguri, and has attacked the military in more remote areas. Hundreds of people have been killed since Buhari's declaration. On Monday, police said three female suicide bombers detonated on the route between Maiduguri and the city of Bama, killing two people and injuring six.

Maiduguri is home to more than a dozen camps for those displaced by Boko Haram's eight-year insurgency. Tens of thousands of people have been killed over the years. The United Nations refugee agency says 1.8 million have been displaced within Nigeria, with roughly one-third of them living in camps.

The insurgency also has spilled into neighboring countries.

"We will not wait till eternity. We are very optimistic that very soon the entire Borno will be safe enough for full habitation," Shettima said.