MADRID (AP) - Gabonese President Omar Bongo, one of the world’s longest-serving heads of state, has been hospitalized in serious condition in Barcelona, Spain’s Foreign Ministry said.

Gabon’s information minister denied Thursday that Bongo was ill, but a statement from the country’s embassy in France later confirmed he was in a clinic in the Spanish city.

A Foreign Ministry official in Madrid would not say what 73-year-old Bongo is suffering from, but said he is in "serious but stable" condition. The official spoke on condition of anonymity in line with ministry rules.

Barcelona’s Quiron Clinic told The Associated Press that Bongo is being treated there. Spokesman Carlos Segui said the hospital is not releasing further information at the request of Bongo’s family.

A Libreville-based African diplomat said Bongo was suffering from diabetes and prostate cancer. He spoke on condition of anonymity because he is not authorized to speak to the media.

Spanish Foreign Ministry Miguel Angel Moratinos, touring in the Balkans, told Barcelona-based newspaper La Vanguardia Wednesday night that Bongo "is very sick."

Bongo has ruled Gabon since 1967, and last year he became the world’s longest-ruling president. The monarchs of Britain and Thailand have been heads of state longer.

Bongo is regarded as one of the so-called "African Big Men," dictators who came to power by the gun and resisted the democratic tide sweeping the continent. After 42 years of rule, he faces remarkably little political opposition in his oil- and timber-rich West African nation, ruling through a mixture of patronage and quiet intimidation.

On May 6, Gabon’s government announced that Bongo was "momentarily suspending his activities" to rest during a mourning period for his wife, Edith Lucie Bongo Ondimba. She died in Rabat, Morocco on March 14 after suffering a yearslong illness, the nature of which has not been disclosed.

Speaking by phone from Libreville, Gabon, Information Minister Laure Olga Gondjout denied Bongo was ill.

"It’s false. I will tell you simply that he is in good health and that, according to our tradition, he is observing a period of mourning following the death of his wife," she said.

"In our tradition when you go into mourning, you pull away from public life," Gondjout said. "When they say that he is sick, it’s pure invention. It’s the fruit of somebody’s imagination."

Gondjout said Bongo’s whereabouts are "a private matter."

But a statement from Gabon’s Embassy in France later Thursday said Bongo was "taking a few days of rest in Spain."

"The president is currently staying at the Quiron Hospital in Barcelona, a medical facility of international renown, to carry out a complete medical exam and undergo appropriate treatment in order to be in the best form to return to Gabon and resume his activities as quickly as possible," the statement said.

It denied reports that Bongo had undergone any surgical procedures and lashed out at speculation surrounding Bongo’s health, calling it "indecent ...and knowingly undertaken to sow trouble among the Gabonese people for destabilizing reasons."

The announcement this month that Bongo was suspending "activities" said his vice president, Didjob Divungi Di Ndinge, would chair Cabinet meetings and represent him at the inauguration of South African President Jacob Zuma, who was sworn in May 9.

According to Gabon’s constitution, the head of the Senate, Rose Francine Rogombe, would assume power and organize presidential elections between 45 to 90 days in the event of Bongo’s death. The Senate chief would not be able to run in vote.

Born Albert Bernard Bongo, the youngest of 12 children on Dec. 30, 1935, Bongo served as a lieutenant in the French Air Force, then climbed quickly through the civil service and assumed the presidency in 1967, after Gabon’s first post-independence leader died. Six years later he converted to Islam and took the name Omar.