(AP Photo/Bebeto Matthews)
The turmoil raises the prospect of violence in a region where neighbors Sierra Leone, Ivory Coast and Liberia all have been hit by years of war.
A group calling itself the National Council for Democracy began announcing its takeover on state-run radio and TV hours after the death of longtime dictator Lansana Conte was made public.
"The government is dissolved. The institutions of the republic are dissolved. ... From this moment on, the council is taking charge of the destiny of the Guinean people," said the coup leader, who identified himself as Capt. Moussa Camara.
Dozens of armed soldiers were seen heading toward the prime minister's office inside the country's presidential compound. They appeared less than an hour after Prime Minister Ahmed Tidiane Souare announced in a state broadcast that he was inside his office and his government had not been dissolved.
Guinea's Army chief of staff Gen. Diarra Camara said the motives of the coup leaders were unclear.
"I think they are in a minority. They are not unanimously backed by the army for the time being. I don't know their real objectives," Camara said.
In his takeover announcement, the coup leader said presidential elections would be held within 60 days and an interim president and prime minister would be appointed. The coup leaders were meeting late Tuesday to decide who would head the interim government, said Aboubacar Sompare, president of the National Assembly.
He said three candidates being considered: coup leader Moussa Camara, army chief Toto Camara and Col. Sekouba Konate, who heads an elite army unit.
The U.S. Embassy in Conakry said there had been no reports of fighting or casualties "but the situation remains fluid and uncertain at this time."
"It's obviously a troubled region and with a history that hasn't always seen those kinds of smooth transitions of power. And so we're keeping an eye on it," White House deputy press secretary Tony Fratto said.
Conte, who was believed to be in his 70s, was only Guinea's second president since it gained independence from France a half-century ago.
He was among the last of the so-called "African Big Men" who came to power by the gun and resisted the democratic tide sweeping the continent. Conte's death Monday leaves a dwindling group, including Gabon's Omar Bongo, who took power in 1967, and Robert Mugabe, who has ruled Zimbabwe since it gained independence in 1980.
Guinea is the world's largest producer of bauxite, used to produce aluminum, and also has gold, diamonds and iron ore deposits. The nation, located at the confluence of several West African rivers, could generate enough electricity to power the region, some analysts say.
But Guinea's economy has rapidly deteriorated and its 10 million people are among the world's poorest. A food exporter at independence, Guinea started importing food as it became crippled by corruption, inflation and high unemployment.
While Guinea has managed to avoid the catastrophic wars that ravaged its West African neighbors, regional experts have warned for years that Conte's death or ouster could send it into turmoil.
Jean-Herve Jezequel, a West Africa scholar in France, warned Tuesday of a "real risk of violence in Conakry."
"Much will depend on whether another strongman emerges or not in the coming days," said Jezequel, who works for the MSF Foundation, linked to the aid group Doctors Without Borders.
Richard Moncrieff, West Africa project director for International Crisis Group, said no successor to Conte was being groomed and no one can legitimately step up without elections. "If a constitutional transition of power is not effected, then it will be bad news for Guinea," he said.
"This seizure of power constitutes a flagrant violation of the Guinean constitution," which calls for the National Assembly speaker to take interim power, the African Union said in a statement.
Conte first took power in a 1984 military coup after the death of his predecessor. As a post-Cold War democracy wave swept the continent, he formed a political party and won elections in 1993. He was re-elected in 1998 and 2003, but all the elections were viewed as fraudulent. Conte also changed the country's constitution to eliminate term limits.
For years, Guineans complained but saw stability as preferable to the bloody civil wars in neighboring Sierra Leone and Liberia, or the fighting in Ivory Coast. But his unpopularity grew in his final years as the economy deteriorated.
The most serious recent challenge to Conte's rule came two years ago as demonstrators called for him to step down and Guinea descended into chaos. Conte responded by declaring martial law and sent tanks into the streets of the capital. Security forces killed dozens of demonstrators.
During the 2003 election, rumors of Conte's failing health circulated in the predominantly Muslim country, with reports he was so ill he did not get out of the car to cast his ballot. That winter, he went on TV to put a stop to the rumors of his death.
"Everybody dies," he told the nation. "Even the Prophet died. I will die when Allah wants me to."
A similar wave of rumors began gathering force two weeks ago, when Conte failed to make his usual televised appearance on the occasion of a major Muslim holiday.
Associated Press writers Maseco Conde in Conakry, Guinea, Angela Charlton in Paris and Katy Pownall in Lagos, Nigeria, contributed to this report. Callimachi contributed to the report from Dakar, Senegal.