Nigeria’s President Muhammadu Buhari has asked the parliament to extend his medical leave in the UK, amid concerns that his health may be worse than officials are publicly saying.

The 74-year-old leader, who has been out of the country for two weeks, was expected to return to Abuja on Sunday.

An official statement said he had been advised by doctors to await the results of a series of tests.

However, it did not say how much extra time would be needed.

There was also no mention of what the medical checks were for.

The main opposition People’s Democratic Party (PDP) has called for more transparency about the president’s condition.

‘Two weeks of rumours’ by Habiba Adamu in Abuja

The failure of President Buhari to reveal the exact length of the additional medical leave in London is worrying many Nigerians.

There have been rumours about the president’s health since he left the country two weeks ago.

He officially handed over affairs of the state to the Vice-President Yemi Osinbajo, a move commended by some experts as a sign of respect to the constitution and the rule of law.

Although things are running smoothly on the surface since Mr Buhari’s departure, his continued absence might not be accepted wholeheartedly by some because of the country’s worsening economic crisis.

After the first medical trip to London, Mr Buhari was heavily criticised by a leading health professional who felt that the president should have stayed and sought treatment at home.

Dr Osahon Enabulele, vice-president of the Commonwealth Medical Association, said it was a “national shame” that Mr Buhari had gone to the UK when Nigeria had many competent ear, nose and throat (ENT) specialists, as well as a National Ear Centre.

Health Minister Osagie Ehanire said Nigerians spent more than $1bn a year on medical tourism, an amount the present government has promised to reduce.

It is not clear how much Mr Buhari’s treatment will cost and who will pay for it. But as the number-one citizen, the state is expected to look after his wellbeing.

However, many Nigerians would not be happy if they realised how much such medical trips dent the country’s already depleted foreign reserves.

‘Completely in the dark’

Analysts say that Mr Buhari’s extended leave could further erode confidence in his administration which is already under pressure due to a weak economy and the conflict with Boko Haram Islamist militants in the north-east of the country.

The country is currently suffering from its worst economic crisis in years, following a sharp fall in the price of oil, its major export.

Businesses and investors complain that the government’s handling of the currency exchange rate has made a bad situation even worse, and there have been demonstrations against the lack of jobs and high inflation.

Some Nigerians are particularly anxious about the president’s health after one of his predecessors, Umaru Yar’Adua, died in 2010 after several months of medical treatment in Saudi Arabia.

During that time, very little information was made public about his condition, leading to a political limbo in the country.

It is the second time in less than a year that Mr Buhari has sought medical assistance overseas. Last June, he spent nearly two weeks, again in London, for treatment for an ear infection

In Abuja, where protests against government policies have been taking place, demonstrators used the occasion to voice their concerns.

One woman complained: “We are completely in the dark.”

And a lawyer added: “Anybody can fall sick but when a president falls sick, it should not be a confidential matter.”

Nigerians have been giving their reaction on Twitter too and have commented on what they see as “double standards” over the issue of medical tourism.