A spokesman for Nigerian President Umaru Yar'Adua says he is being treated for a heart condition.
Olusegun Adeniyi told reporters in Abuja Thursday that Mr.Yar'Adua is suffering from acute pericarditis, an inflammation of the membrane around the heart.
He said the president is responding "remarkably well" to treatment for the illness at a hospital in the Saudi city of Jeddah.
The Nigerian president was flown there for tests and treatment on Monday. The spokesman says Mr. Yar'Adua had started complaining of severe chest pain on Friday.
This is the third time the president has gone to Saudi Arabia since August.
The 58-year-old Mr. Yar'Adua is known to suffer from a chronic kidney ailment. Kidney failure is one of the factors that can cause pericarditis.
Mr. Yar'Adua has served as Nigeria's president since winning a disputed 2007 election. Critics have questioned whether he is fit to lead Africa's most populous nation.