Two explosions at a crowded market in northeastern Nigeria have killed more than 60 people, sources told Al Jazeera.
The twin bomb blasts on Tuesday hit the Monday market in Maiduguri, the capital of Borno state, the sources said.
"After the first explosion happened and people started to gather, a second explosion took place," Al Jazeera's Rawya Rageh, reporting from Abuja, said.
"Many people are saying that they believe the second explosion was carried out by a female suicide bomber. At least that is what an initial reports are indicating."
Soldiers and police officers cordoned off the area while rescue workers helped survivors to the hospital.
Hospitals have been flooded with injured residents, Al Jazeera sources said.
No official statements have been issued yet.
Maiduguri is a stronghold for the armed group Boko Haram. Borno state is one of the three states in northeastern Nigeria that are under a state of emergency because of the extremist violence.
Also on Tuesday, government and security sources told AFP that Boko Haram had taken over another town in Nigeria's northeast.
Maina Ma'aji Lawan, who represents Borno in Nigeria's senate, said the group was in control of the border town of Damasak.
Nigerian soldiers and hundreds of residents fled across the frontier to seek sanctuary when the heavily armed fighters opened fire on traders on Monday morning, he said.
"There is not a single male in Damasak," Lawan said. "Boko Haram is in control because all males and soldiers have fled."
Boko Haram has seized more than two dozen towns in Borno and neighbouring Yobe and Adamawa states, marking a change in strategy from its previous trademark of deadly hit-and-run strikes or high-profile strikes against government, police or military targets.
The group wants to create an Islamic state in northeastern Nigeria, and its seizure of towns has raised fears about a potential loss of government control in the region.