The Nigerian air force has claimed to have killed at least three senior commanders of Boko Haram in a series of airstrikes.

It claims the group's elusive leader, who has a bounty on his head, has been fatally wounded in the raids which were launched on Friday.

Government planes attacked Boko Haram fighters in the village of Taye, inside the Sambisa forest in Borno State.

"Their leader, so called 'Abubakar Shekau', is believed to be fatally wounded on his shoulders," army spokesman Colonel Sani Kukasheka Usman said in a statement.

He confirmed the deaths of three Boko Haram commanders - Abubakar Mubi, Malam Nuhu and Malam Hamman - and said several others were wounded in the attack on the Islamist group's northeastern forest stronghold.

The military has claimed to have killed the Boko Haram leader in the past, only to have a man purporting to be him appear later, apparently unharmed, ridiculing suggestions of his death in video statements.

There was no immediate reaction from the terror organisation.

Nigerian forces, with the support of regional troops, have recently recaptured swathes of territory lost to the jihadists.

The air raid claim comes ahead of US Secretary of State John Kerry's visit to the country this week, for talks likely to focus on the challenges of tackling Boko Haram.

The group, seeking to impose strict Islamic law in the country's mainly-Muslim north, has killed some 20,000 people and displaced as many as 2.6 million others who have been forced to flee their homes since 2009.

It kidnapped 270 schoolgirls in April 2014, some of whom it is believed are being held in Sambisa forest.

The group released a video on YouTube last week, claiming to show some of the girls taken from the town of Chibok two years ago.

It also claimed some of the children had been killed in government airstrikes.