Nigeria’s ailing President Muhammadu Buhari has written to his Guinean counterpart Alpha Conde to thank him for the nationwide prayers he had organised for his recovery, his spokesman Femi Adesina has said

Mr Buhari, 74, has been in the UK for almost 80 days, receiving treatment for an unspecified illness.

In his letter, Mr Buhari assured Mr Conde – the current chairman of the African Union – that he was making “good progress”, and would return to Nigeria to resume his presidential duties as soon as his doctors gave him the go-ahead, Mr Adesina said.

In an earlier letter, Mr Buhari had also accepted his nomination as leader of the “2018 AU Theme on the Fight Against Corruption”, Mr Adesina added.

“I wish to express my readiness to accept this new important role and to reiterate my commitment to contribute towards our collective efforts to strengthen good governance and development on the continent,” Mr Buhari said in the letter.

He was nominated for the role at the summit of AU leaders in Ethiopia on 4 July.

Mr Buhari’s long absence has caused some anxiety in Nigeria, and has led to speculation that his rivals were plotting to succeed him.