By Marco Trujillo
BARCELONA (Reuters) - Gabon's President Omar Bongo, Africa's longest-serving leader, died on Monday of a heart attack in a Spanish clinic after more than four decades in power in the central African oil-producing nation.
The 73-year-old leader died at around 2:30 pm (1:30 p.m. British time) in the Quiron clinic in Barcelona, according to a statement issued at the hospital by Gabonese Prime Minister Jean Eyeghe Ndong.
"Throughout his political career, President Bongo always cultivated unity and cohesion among the Gabonese people," Ndong said, announcing 30 days of national mourning.
"At this moment of grief, the government calls on you to remain united in solidarity, in contemplation and dignity," he said in the statement.
Bongo's death leaves a political void in the nation he tightly controlled.
The government said it would respect the terms of the constitution, under which Senate President Rose Francine Rogombe, a Bongo ally in the ruling Gabonese Democratic Party (PDG), is expected to take over as interim leader.
She should then organise elections within 45 days.
French President Nicolas Sarkozy paid tribute to a "faithful friend of France" who he said had "won the esteem and respect of his peers, particularly through his numerous initiatives to support peace around the African continent."
"France, faithful to its long friendship, remains by the side of Gabon, by its institutions, and by its people at this testing time," the French president said in a communique.
SON GROOMED FOR POWER
Concerns over Bongo's health grew last month after he suspended his functions as head of state for the first time since taking power in 1967.
Bongo checked into the clinic in Barcelona in May, officially to rest after the sudden death of his wife. But reports that he was seriously ill fuelled speculation over who would lead the country if he died.
Although there have been some concerns about stability, analysts say that the ruling party is likely to tightly manage the transition and that Bongo's successes in easing ethnic tensions will reduce the risk of turmoil.
Gabon's opposition say Bongo's son, Defence Minister Ali Ben Bongo, is being groomed to step in and question whether elections would be fair. Analysts also see him, or another close family member, as most likely to take over.
"Thirty days of mourning will give them time to work out what will happen and whether there will be some sort of election process, presumably to favour Ali Ben Bongo," said Kissy Agyeman-Togobo, Africa analyst at IHS Global Insight.
Gabon has maintained close ties with former colonial ruler France and attracted investors with a Eurobond as well as its long-established oil industry. France's Total is one of the country's biggest investors.
Oil output is in decline but oil revenues still account for about half of the country's income, even though they have been hit by falling world energy prices.
The country also has a $1 billion (624.3 million pound) Eurobond, which is due to mature in 2017, and which the government is in the process of buying back. Credit rating agency Standard and Poors reaffirmed the country's existing credit rating and said the outlook was stable.
(Additional reporting by Linel Kwatsi in Libreville and Vanessa Romeo in Barcelona; Writing by David Lewis and Nick Tattersall; Editing by Giles Elgood)
