Nigerian President Muhammadu Buhari, who is in Britain for health checks, has asked parliament to extend his medical leave. 

Mr Buhari left Nigeria two weeks ago and had been expected to return to Abuja today. 

In a statement, his office said he'd been advised by doctors to complete and await the results of a series of tests.   

His aide Malam Garba Shehu said he was not in a critical condition and had not been admitted to hospital but he did need to undergo further tests. 

Mr Shehu, who was speaking with the BBC, refused to reveal the nature of the president's health problems.