CONAKRY, Dec 23 (Reuters) - Guinea announced on Tuesday the death of its long-serving president, Lansana Conte, and hours later a military officer made a broadcast on state radio saying the constitution and government were suspended.

In the radio broadcast, Captain Moussa David Camara said a self-styled National Council for Democracy was taking over.

The broadcast created confusion in the seaside capital Conakry after government leaders said earlier Conte had died following nearly a quarter century of rule over the West African state, the world's leading exporter of bauxite aluminium ore.

Soldiers and police guarded the presidential palace and the central bank, witnesses said.

Journalists at state radio headquarters contacted by Reuters said a group of soldiers had entered the building and forced staff to broadcast the communique.

The statement read on the air by Capt. Camara said the constitution was suspended and the government dissolved. A transitional council of military and civilian members would be created in the coming days which would reflect "ethnic balance".

The broadcast cited what it called widespread corruption, impunity and anarchy and a "catastrophic economic situation" to justify the dissolving of the government. "The members of the current government are in large part responsible for this unprecedented economic and social crisis," it said.

The death of Conte, a diabetic, chain-smoking general, left a potential power vacuum.

Guinea has experienced anti-government riots and strikes and bloody military mutinies in recent years, aggravated by rising prices of food and fuel. Most of the population are poor, despite the nation's huge mineral riches.

When government leaders gathered to announce Conte's death on state television in the early hours, Armed Forces chief General Diarra Camara ordered troops to protect strategic locations and the borders of the former French colony.

National Assembly President Aboubacar Sompare, accompanied during the broadcast by Prime Minister Ahmed Tidiane Souare, Camara and other officials, said Conte had died on Monday night. Conte was believed to be 74.

Sompare asked the country's Supreme Court to name him president in line with the constitution.

Article 34 of Guinea's constitution foresees the national assembly president taking over in the event of the death of the head of state and organising presidential elections in 60 days. Legislative elections were already planned for 2009.

"I have the heavy and difficult task to inform you with great sadness of the death of General Lansana Conte, President of the Republic of Guinea," Sompare said in the television broadcast.

ROLE OF MILITARY

As the television played Guinean music, Sompare declared 40 days of national mourning in the world's number one exporter of bauxite, the ore from which aluminium is made.

Although rumours that Conte was seriously ill had circulated in the dilapidated seaside capital Conakry for days, the government chose the early hours, when most people were sleeping, to announce his death. The streets were calm.

Conte, who said he was born around 1934, had governed Guinea since 1984 when he seized power after the country's first president, Sekou Toure, died in a U.S. hospital.

But he never groomed a clear successor. "I arrived as a soldier, and I will finish as a soldier ... God gives and takes life -- end of story," Conte once said.

Analysts said the way in which the military, a key pillar of support for Conte's rule, reacted to the news of his death would be crucial to the future stability of the country, where major international mining companies have operations.

"The military obeyed Conte ... and now he's not there," one veteran local journalist told Reuters on condition of anonymity. The armed forces are known to be split by generational and ethnic divisions.

Conte, who became reclusive in his later years of rule, had suffered health problems for years, including sometimes collapsing in public. He often travelled abroad for medical treatment in Morocco, Cuba and Switzerland.

Veteran opposition leader Jean Marie Dore of the Union for the Progress of Guinea party, a fierce critic of Conte, said he was saddened by the death of a man he called a "compatriot".

"The most important is what is to come: It is essential that the institutions function correctly and that the provisions of the constitution be respected," said Dore.

Last year, a general strike triggered anti-government riots in which more than 180 people were killed, most of them shot by Conte's forces, according to witnesses and human rights groups.

Units of the army and police staged violent mutinies this year to demand payment of back pay and other benefits.

Foreign companies with operations in Guinea include Alcoa, Rio Tinto Alcan and Russia's RUSAL.