Troops deposed the government in this island nation off West Africa (search) on Wednesday, a revolt that could change control of the impoverished country's new oil wealth.

The rebellious soldiers said they would install a military junta to govern Sao Tome (search) and Principe (search), one of Africa's smallest and poorest countries.

The uprising renewed concern over political stability in the Gulf of Guinea at a time when the West African region grows in importance as an alternative to the Middle East as a source of oil.

Sao Tome, a former Portuguese colony of about 140,000 people, has courted the United States in recent years in the hope of aid and support for offshore oil exploration.

Troops detained Prime Minister Maria das Neves and other senior officials but there were no reports of casualties in the coup, which began with pre-dawn gunfire. President Fradique de Menezes was on a visit to Nigeria at the time.

"I am now making a strong appeal to all democrats, world leaders and African leaders to help us stop this kind of procedure," Menezes said in Abuja, Nigeria, where he was a summit with other regional leaders.

Menezes, a wealthy former businessman and lawmaker, was elected to a five-year term as president in July 2001. He appointed Neves to her post in October 2002.

In Washington State Department spokesman Richard Boucher deplored the military takeover.

"We strongly urged those involved to release the arrested government officials," Boucher said.

He said that the United States was examining humanitarian and military aid to Sao Tome and Principe, which could be suspended if the government has been overthrown.

Nigerian President Olusegun Obasanjo denounced the coup, saying "We strongly condemn this action and call on the military adventurists to hand over power."

The president of Senegal, Abdoulaye Wade, said he expected the African regional body ECOWAS to take some action to restore Menezes to power, though he gave no specifics.

Claudio Corallo, the honorary Italian consul in Sao Tome, said during a visit to Italy that he had spoken to family and friends at home who described the country as calm. "It appears as if everything is under control," he said. "There were no casualties."

Government ministers were held at the main army barracks in Sao Tome, the capital. About 30 lawmakers were freed after being detained at police headquarters for several hours.

The rebellious soldiers also seized the airport and key government buildings.

In a statement read on state radio, the soldiers said they acted "due to the continuing social and economic decline of the country."

They pledged not to harm the officials in detention.

Maj. Fernando Pereira, an artillery officer who first acted as spokesman for the mutineers and was later described as the coup leader, announced a curfew beginning at 7 p.m.

The streets of the capital were calm Wednesday afternoon and the two main markets opened for business after sporadic gunfire in the morning. The gunfire apparently was warning shots and the renegades met no armed resistance.

Portugal's ambassador, Mario de Jesus Santos, met with Pereira and said the mutineers told him they are not seeking power.

The soldiers decided to act "when the living standards of the people went into a steep decline," Santos told Portugal's national news agency Lusa.

Though the islands are rich in natural beauty, they are desperately short of development projects. The islands mainly attract fishermen goring after marlin and small groups of tourists.

Sao Tome and Nigeria initially squabbled over who owned oil reserves found five years ago in the Gulf of Guinea, then agreed to share them.

West Africa is becoming an increasingly important oil supplier to the United States.

Although the government has sought to dampen excessive optimism, the little country has been gripped with oil fever.

The United States imported 25.1 million barrels of oil -- 8.5 percent of its total crude imports -- from the Gulf of Guinea in April, according to the most recent statistics compiled by the U.S. Energy Information Administration.

The U.S. suppliers in the region were Nigeria, Gabon and the Ivory Coast. Saudi Arabia remained the single largest foreign source of crude that month, supplying 61.2 million barrels, or 20.8 percent of U.S. oil imports, the Energy Information Administration said.

Major oil companies are bidding for contracts to develop the oil fields. Winners of the contracts are to be announced later this year.

An official at the Nigeria-Sao Tome Joint Development Authority, which is handling the bids, said on condition of anonymity that ExxonMobil, Royal/Dutch Shell, ChevronTexaco and TotalFinaElf were among companies that have indicated interest.

Last year, U.S. Gen. Carlton Fulford, deputy commander in chief of the European Command, visited Sao Tome for what were called planning talks on security in the Gulf of Guinea. His visit was seen as an indication of Washington's interest in Sao Tome.

The discovery of oil beneath the Atlantic seabed has already caused trouble, even though it will be several years before rigs begin pumping.

The initial feud between Sao Tome and Nigeria over who owned the offshore reserves gave way to squabbling between political parties in Sao Tome over how to develop the industry and where the benefits should be applied.

"We want to learn lessons from other Africa countries that have suffered because of oil," Rafael Branco, the deposed oil minister, told The AP in January. "Oil is only important insofar as oil income can create a basic infrastructure."

Since President Menezes began his term in September 2001, he has fired four prime ministers and dissolved Parliament once.

In January, Menezes revoked a decree that called for early elections and the dissolving of Parliament after striking a deal with lawmakers eager to trim his powers.

In April, Menezes admitted receiving $100,000 from Environmental Remediation Holding Corporation, an American oil company involved in offshore exploration in Sao Tome. He denied any wrongdoing.