Nigeria's military says it carried out airstrikes Thursday that struck Boko Haram bases in the northeast and killed a "large number" of the militants.

The military says in a statement that the Nigerian Air Force targeted Boko Haram training camps and weapons dumps in the Sambisa Forest and the town of Gwoza, two Boko Haram strongholds.

It says that after the strikes, many militants were fleeing their bases. There has been no independent confirmation of the military's claims.

Sambisa is where Boko Haram took more than 200 schoolgirls after kidnapping them from the village of Chibok in April 2014. The vast forest stretches into parts of five Nigerian states and has been a hideout for the Islamic extremist group for several years.

The girls remain missing more than 10 months after their abduction. Nigeria reported more success against Boko Haram on Wednesday, saying its forces had killed more than 300 militants and retaken 11 towns from the group since Monday.

The statements are hard to verify due to fighting and the destruction or shutdown of mobile phone service in much of the northeast.

Earlier this week, Boko Haram's leader Abubakar Shekau threatened to derail Nigeria's elections, which were already postponed until next month because of insecurity. The militant group has repeatedly warned Nigerians not to vote in the presidential and parliamentary elections, now set for March 28.

Witnesses said Boko Haram fighters burned down much of a town in Borno state (Askira Uba) on Sunday and Monday. On Tuesday, bombs went off at three locations around Nigeria, causing dozens of casualties.

The extremist group, whose name means "Western education is forbidden" has killed thousands of Nigerians in the past five years in attacks on schools, towns, markets, churches, mosques and various government targets.

During 2014, the militants seized numerous towns in the northeast for what Shekau calls a caliphate. Fighting has intensified in the past month, after Niger, Chad, and Cameroon all deployed troops against the militants.