Africa's longest-serving leader, President Omar Bongo of Gabon, has died at the age of 73, French media say. Mr Bongo had been treated in a clinic in the Spanish city of Barcelona. He was reported to have cancer, and had suspended his activities in May. There is no official confirmation of the reported death. Gabon's prime minister said he was "not aware" of it. Mr Bongo has led the oil-producing state since 1967, and faces a French inquiry into corruption allegations. The death of the Gabonese veteran leader was reported by AFP news agency, who quoted a French government source, and also by the website of French magazine Le Point, quoting a source close to Mr Bongo's entourage. But later Prime Minister Jean Eyeghe Ndong told Gabonese TV that he had been "very surprised" to read the reports. "If such a situation comes about, I would think that the president's family would naturally get in touch with me," he said. 'Powerful dynasty' Mr Bongo became vice-president in 1967, taking over as head of state later that year after the death of Gabon's first post-independence President, Leon Mba. Mr Bongo is one of three African leaders being investigated for alleged embezzlement by a French judge - the others are Denis Sassou-Nguesso of the Republic of Congo and Teodoro Obiang Nguema of Equatorial Guinea. It is alleged that the properties owned by Mr Bongo's family in France could not have been purchased with official salaries alone. Mr Bongo denied any wrongdoing. Analyst say he has built a powerful dynasty in the former French colony during his years in office. Opposition leaders have claimed his son, Ali-Ben Bongo, currently defence minister, is being manoeuvred to take over. In 1973, Mr Bongo converted to Islam, changing his name to El Hadj Omar Bongo. His wife, Edith Lucie Bongo, President Sassou-Nguesso's daughter, died in March 2009. Source: BBC