The Nigerian military says soldiers have retaken the town of Gwoza, one of the last areas in northeastern Nigeria controlled by militant group Boko Haram.
The military says on Twitter that troops captured the Borno state town on Friday morning and destroyed the headquarters of Boko Haram's self-declared caliphate. It said more details would follow.
U.S. intelligence officials expressed caution about the report, saying that even if the militants had retreated, it did not necessarily mean they were near defeat. Intelligence officials told VOA that Boko Haram has used strategic retreats in the past, only to wait, sometimes for weeks or more, for an opportunity to counterattack.
The unconfirmed report came out 24 hours before Nigerians go to the polls for presidential and parliamentary elections.
President Goodluck Jonathan and the ruling PDP party are facing a tough challenge from the opposition APC and its presidential candidate, former military ruler Muhammadu Buhari. Polls have indicated the race is too close to call.
Jonathan urges peaceful vote
In a nationally televised address Friday, Jonathan commended the armed forces and called on all Nigerians to refrain from violence.
He said, "The nation's security agencies are also fully prepared and ready to deal decisively with any group or persons who attempt to disrupt the peaceful conduct of the elections or cause any form of public disorder."
On Thursday, both Jonathan and retired General Buhari pledged to respect the outcome of the election as long as it is "free, fair and credible."
Past elections have been marred by allegations of voting fraud. Violence after the 2011 elections killed some 800 people.
Nigeria's Independent National Electoral Commission is hoping to prevent fraud this time around with a new biometric voter identification system.
The vote was delayed from mid-February because of fighting and insecurity in the northeast, where the Boko Haram insurgency has raged since 2009.
Nigerian forces, aided by foreign mercenaries and troops from Chad, Niger and Cameroon, have pushed the Islamic extremists out of nearly all the towns the group once controlled in Borno, Yobe and Adamawa states.