Nigerian president Muhammadu Buhari has publicly announced that he is going to London for medical checks.

The news came immediately after he met a group of 82 Chibok girls freed from Boko Haram extremists.

A thin-looking Mr Buhari, 74, had welcomed the Chibok girls at his official residence on Sunday evening, a day after they were released.

President Buhari has missed three weekly cabinet meetings and he spent about six weeks in London on medical leave earlier this year, later saying that he had never been as sick in his life.

The cause of his illness is unclear but a statement from his office said there was "no cause for worry" and that the length of his London stay would depend on advice from doctors.

One of his advisers, Femi Adesina, said: "The president was delighted to receive them and he promised that all that is needed to be done to reintegrate them into the society will be done.

"He promised that the presidency will personally supervise their rehabilitation."

Meanwhile, it was also revealed that the girls were released in exchange for five Boko Haram fighters who were being held by Nigerian authorities, as part of a deal brokered by the International Committee of the Red Cross and the Swiss Government.

They are now with government officials in Nigeria's capital Abuja, where they will be rehabilitated before returning to their parents, many of whom do not know whether their daughters are among those freed.