Nigerian forces backed by air strikes seized the northeastern border town of Baga from Islamist militant group Boko Haram on Saturday, the military said.
"We have secured Baga. We are now in full control. There are only mopping up exercises left to do," Defense Spokesman Major-General Chris Olukolade said by telephone.
In a statement minutes earlier Olukolade said that "a large number of terrorists had drowned in Lake Chad" as troops advance on Baga.
Baga is at Nigeria's border with Chad, Niger and Cameroon and it was the headquarters of a multinational force comprising troops from all four countries, so its recapture was an important victory for Nigeria.
"Not even the strategy of mining over 1,500 spots with land mines on the routes leading to the town could save the terrorists from the aggressive move of advancing troops," Olukolade had earlier said in a statement.
Boko Haram fighters in many parts of Nigeria and the region are on the run, after being subjected to a major military offensive on all sides by Nigeria and its neighbors Chad, Cameroon and Niger.
Troops had captured five anti-aircraft guns and 34 motorcycles while five of the militants' trucks had been destroyed, Olukolade said.
A spokesman for Chad's army said his troops did not participate in the Baga offensive.