Gabon's President Omar Bongo, Africa's longest-serving ruler, died Monday morning, the country's prime minister said, settling conflicting reports from government and media accounts. Calm was reported after the announcement, but Gabon's Ministry of Defense nonetheless announced it was closing all of the country's land, air and sea ports, according to a ministry statement quoted by CNN. The statement, which was broadcast on state television and radio, said that in "the best interest of the nation, the Ministry of Defense calls on the population to increase their vigilance and patriotism during this difficult and painful time the country is facing." In a statement, Prime Minister Jean Eyeghe Ndong said Bongo suffered cardiac arrest at a hospital in Barcelona, Spain. "He dedicated his political life to his country and the Gabonese people, always cultivating the unity and cohesion of the Gabonese toward a true peace," Ndong said. The government declared a 30-day national period of mourning. Bongo, 73, had been receiving treatment for intestinal cancer at the Quiron clinic in Barcelona, Spain, according to the Gabonews agency.