The president of Togo (search), Africa's longest-ruling leader, died after suffering a heart attack on Saturday. Hours later, the military announced his son would take his place as head of state.

President Gnassingbe Eyadema (search), 69, suffered a heart attack early Saturday in his hometown of Piya in southeastern Togo and died on his way to Europe for treatment, officials said.

Speaking on state radio, Prime Minister Koffi Sama (search) confirmed the death and called upon the security forces to keep law and order. He also announced all land and air borders to the West African nation of 5.5 million people had been closed.

"The armed forces and police must help preserve peace and national security," Sama said. "All the country's political, social, religious leaders must avoid any act likely to plunge the country into anarchy and confusion."

State TV broadcast images later showing the country's top military brass, including army chief of defense staff Gen. Zakari Nandja, swearing an oath of allegiance to Faure Gnassingbe (search), Eyadema's son, as "the acting president."

Togo's constitution calls for the speaker of parliament to succeed the president in the event of his death. By law, the parliament speaker must call national elections to choose a new president within 60 days.

Nandja, however, said the speaker of parliament, Fanbare Tchaba, was out of the country and the military had declared Eyadema's son president to ensure stability. Nandja did not say whether the move was a temporary measure and it was not known where Tchaba was.

"The armed forces of Togo finds itself faced with the evidence of a total vacuum of power in Togo. This is because the speaker of the national assembly is absent, outside the country," Nandja said. "Therefore, in order not to create a power vacuum, the armed forces of Togo has decided to declare Faure Gnassingbe the head of state."

Faure Gnassingbe was the country's minister of mines and communication. Family names are often reversed in Africa.

Eyadema, a former Togolese French Foreign Legion officer, has ruled Togo since 1967, when he came to power following Africa's first postcolonial coup. Only Cuba's Fidel Castro has been in power longer.

Though last re-elected in a May 2003 vote, Eyadema was considered one of Africa's last "Big Men" — rulers holding power through patronage, the loyalty of their ethnic and regional groups, and military force.

He was believed to have heart problems, but the state of his health was not made public. Two weeks ago, he traveled to Switzerland for what authorities said was a medical checkup.

State radio played mourning music, interrupted by Sama's comments.

Barry Moussa Barkue, special adviser to the president, said the death was unexpected. He said Eyadema looked "hearty and even granted audience to visitors" on Friday. "So his sudden death is unbelievable."

Dama Dramani, secretary general of the ruling Togo People's Rally party, described the death as "tragic for Togo."