In a tweet on Monday, Nigerian defense spokesman Chris Olukolade said the town of Goniri in Yobe state had been liberated from the terrorist group.

"That was the last stronghold of terrorists in Yobe... #YobeIsFree," Olukolade wrote.

In a later tweet, the defense spokesman also confirmed that the Nigerian military had claimed victory in Bama.

"Nigerian troops have this afternoon routed terrorists from #Bama in #Borno state. Mopping up operation is ongoing," he tweeted.

In an official statement, Olukolade said the recapture of Bama had inflicted "massive" casualties on the militants.

Bama, the second-biggest town in the troubled Borno state, was seized by Boko Haram in early September during the rapid capture of several towns and villages in northeastern states of Borno, Adamawa and Yobe. The Islamists continued to widen their attacks into neighboring Chad, Cameroon and Niger.

In total, Boko Haram's violent insurgency has killed more than 13,000 people since 2009, and and displaced 1.5 million. Earlier this month, the terrorist group also pledged their allegiance to the "Islamic State" terrorist group.

In response to the insurgency, a four-country joint offensive has been launched which has seen a wave of success in rebel-held territory in recent weeks.

The military operation is part of efforts to secure and stabilize northeast Nigeria in time for a general election set for March 28.

ksb/cmk (AFP, AP)