(CNN) Gabons President Omar Bongo Africas longest-serving ruler has died after a battle with cancer, the countrys official news agency reported Sunday. He was 73. Bongo took power in 1967, seven years after the West African countrys independence from France. He had been receiving treatment for intestinal cancer at the Quiron clinic in Barcelona, Spain, the state news agency GNA reported. Bongo imposed one-party rule a year after succeeding the countrys first president, who died in office. He allowed multiparty elections after a new constitution in 1991, but his party has retained control of the government since then.