President Umaru Yar’Adua flew back to the capital Abuja unannounced in the early hours of Wednesday, his plane met on the tarmac by a white ambulance.

A weekly Cabinet meeting went ahead after a delay of several hours after it became clear that Yar’Adua would not be attending.

Acting President Goodluck Jonathan will remain in charge while the president, treated for a serious heart condition, continues to recuperate, the president’s spokesman Segun Adeniyi said.

“After being discharged by the team of medical experts overseeing his treatment ..., President Yar’Adua returned to the presidential villa, Abuja early this morning,” he said. “While the president completes his recuperation, Vice President Jonathan will continue to oversee the affairs of state,” he added. The two leaders had yet to meet after Yar’Adua’s return, Information Minister Dora Akunyili told reporters after the Cabinet meeting.

She said Jonathan had been briefed of Yar’Adua’s return by presidential aides.

Recent reports “continue to suggest that Yar’Adua’s health remains fragile and that he may still be unable to fulfill the demands of his office,” said Washington’s top envoy to Africa, Johnnie Carson.

“We hope that President Yar’Adua’s return to Nigeria is not an effort by his senior advisers to upset Nigeria’s stability and create renewed uncertainty in the democratic process,” Carson said in a statement released by the US Embassy in Lagos.

“Nigeria needs a strong, healthy and effective leader to ensure the stability of the country and to manage Nigeria’s many political, economic and security challenges. Nigeria is an extraordinarily important country... and all of those in positions of responsibility should put the health of the president and the best interests of the country and people of Nigeria above personal ambition or gain.”

An AFP correspondent saw two planes land in succession — one of them believed to be an air ambulance — amid heavy security at the presidential wing of the international airport in Abuja.

A white ambulance and several sports utility vehicles with black tinted windows drove to meet the plane.

Soldiers were deployed at strategic points along the airport road.

A convoy of 23 vehicles — including the ambulance — accompanied by a full presidential escort left the airport and was seen driving toward the direction of Yar’Adua’s official residence, Aso Rock Villa.

The president was taken ill last November and underwent treatment for pericarditis, an inflammation of the membrane covering and protecting the heart.

He has not been seen in public since then and has only given one brief interview.

Yar’Adua had made no provision for who should take charge during his lengthy absence from the helm of a major oil exporter.

Some of the tension was eased when Parliament voted on Feb. 9 to hand over power to Jonathan.

He moved swiftly to assert his authority, including conducting a Cabinet reshuffle.

Yar’Adua’s loyalists were initially reluctant for a transfer to be formalized but a split emerged in Cabinet ranks as international powers, including the European Union and United States, voiced their unease.

Jonathan’s elevation won widespread international support, including from the African Union, which warned the army to support the handover.