Nigeria's military on Saturday claimed the killing of scores of Boko Haram insurgents and the rescue of 20 more hostages during an operation in the notorious Sambisa forest, an Islamist stronghold.

"Despite continuous encounter with large number of land mines which still litter the Sambisa forest, troops have forged ahead...as scores of the terrorists died in the assault on their bases on Friday," a defence ministry statement said.

"A total of 20 women and children were rescued at the end of the Friday operation," in the forest in the country's northeast, it added.

One soldier died while 10 others were wounded in the assault on rebel bases, according to the statement.

There was no way to independently verify the military's claims.

The defence ministry's accounts of clashes with Boko Haram have in the past not been consistent with eye witness reports.

But Nigeria has reportedly won a series of successes over the insurgents in recent weeks.

More than 700 hostages, primarily women and children, have reportedly been freed during the military's assault on Sambisa, which Boko Haram has used as a base for several years.

According to Amnesty International, the extremists have kidnapped more than 2,000 women and girls since the start of last year. Many female hostages were victims of sexual violence while in captivity.

Nigeria's latest assault on the insurgents has been backed by troops in neighbouring Chad, Cameroon and Niger.

Despite the apparent successes, attacks have continued, including a surge in violence this week in northeastern Adamawa state, which has been relatively quiet for months.

Experts believe that while Boko Haram has been flushed out of dozens of towns it previously controlled, the group will continue to launch guerilla-style attacks, particularly targeting defenceless civilians.