LIBREVILLE, Gabon - Omar Bongo, whose nearly 42-year rule of Gabon was a throwback to an era when Africa was ruled by "Big Men," died yesterday. He was 73.

The government responded to Bongo's death at a hospital in Spain by closing Gabon's airport and its borders. Security forces took up positions in front of government buildings and electrical installations in Libreville, the capital.

Gabon's constitution calls for the Senate leader to assume power and organize presidential elections within 90 days of Bongo's death. But there has been speculation that one of Bongo's sons - who is now minister of defense - would try to seize power.

Since the president had checked into the Spanish hospital last month, Gabonese officials had aggressively denied that he was ill.

Bongo, who was believed to be one of the world's wealthiest leaders, had kept a tight grip on power in the oil-rich former French colony since he became president in 1967. Opposition parties were only allowed in 1990, amid a wave of pro-democracy protests.

Bongo had kept his country remarkably peaceful and governed without the sustained brutality characteristic of many dictators.

Bongo, meanwhile, amassed a fortune that made him one of the world's richest men, according to Freedom House, a private Washington-based democracy watchdog organization.

Born Albert Bernard Bongo on Dec. 30, 1935, the youngest of 12 children, Bongo served as a lieutenant in the French Air Force, then climbed quickly through the Gabonese civil service, eventually becoming vice president. He assumed the presidency Dec. 2, 1967, after the death of Leon M'Ba, the country's only other head of state since independence from France in 1960.

Bongo set up a one-party state. Six years later, he converted to Islam and took the name Omar.

His presidential security staff numbered 1,500, according to the U.S. State Department, while the entire military numbers just 10,000 troops.

French President Nicolas Sarkozy expressed his "sadness and emotion" at Bongo's death yesterday.

Gabon ranks fifth among sub-Saharan African countries in oil exports. But oil dependency means the country has more oil pipeline (886 miles) than paved roads (582 miles). Only 1 percent of its land is cultivated and Gabon produces virtually no food. Instead, basics such as tomatoes are imported from France and neighboring Cameroon, pushing prices so high that Libreville, the capital, is the world's eighth most expensive city, according to Employment Conditions Abroad International. *