Gabon's Constitutional Court will formally announce a vacancy in power following Monday's death of long-time president Omar Bongo.   It is the first step toward new elections expected before the end of July.

The government's move to have the court declare a vacancy in power clears the way for Senate President Rose Francine Rogombe to serve as interim leader.  A Bongo ally in the ruling Gabonese Democratic Party, she will have 45 days to organize new elections.

Among those thought to be potential candidates for that vote are Vice President Didjob Divungi Di Ndinge, the late president's son, Defense Minister Ali Ben Bongo, and the defense minister's brother-in-law, Foreign Minister Paul Toungui.

Defense Minister Bongo is calling for calm and "quite contemplation" to preserve the unity and peace which he said was so dear to his father.

In a statement on national television, he said he was speaking for the Bongo family, not as a government official.  In these difficult circumstances, he said, "love of one's homeland should give one pause and constitute a sacred duty for all children of Gabon."

The government has announced 30 days of mourning for the man who was Africa's longest-serving head of state.  He died in a Spanish clinic at the age of 73.

Gabon's defense ministry has closed all air, land and sea borders.  A statement said sensitive government buildings have been secured and defense forces are in place across the country.

Security forces patrolled Libreville overnight, where the mayor has banned large gatherings and ordered all bars and nightclubs closed.  Most shops and markets opened Tuesday, but Internet access to the country remains cut.

Oil revenues have fueled steady economic growth, accounting for 80 percent of export income and giving Gabonese one of the highest per-capita incomes in sub-Saharan Africa.  But that wealth has been shared unevenly, with the United Nations estimating that as much as 70 percent of the population live below the poverty line.

President Bongo largely succeeded in bridging Gabon's ethnic differences by recruiting political opponents to join his government.

That stability led the credit rating agency Standard & Poors to hold Gabon's debt rating steady, following the president's death.  A statement from the agency says it believes Gabon's political stability will remain underpinned by the absence of ethnic tensions, the lack of armed factions, and the presence of more than 1,000 French troops.