Citizens of this West African country were banned from leaving their homes on Tuesday as a curfew went into effect in Guinea, but sporadic gunfire was reported and youths attempted to restart protests that have killed dozens in recent days.

President Lansana Conte declared martial law late Monday. The move followed three days of rioting and clashes with security forces left at least 27 dead in Guinea as opposition leaders and major trade unions called for Conte to step down after his apparent violation of a power-sharing agreement.

"They are still firing heavy arms. I didn't sleep all night because of the shooting," said Aissatou Diallo, a resident of the Madina neighborhood. "I see from my balcony people walking in the streets who are going to buy and sell things in the market. I even see some taxis."

In the outlying neighborhood of Dar-es-Salam, Alpha Oumar Bah said groups of youths started to gather again Tuesday morning, but ran off after soldiers arrived, shooting into the air.

The U.S. embassy ordered all staff family members to leave Guinea. The embassy urged private U.S. citizens to depart as well.

In an e-mail sent by the consular warden, the embassy offered seats to eligible family members and American citizens on a U.S. government plane flying to Dakar, Senegal. The warden said the plane was not an evacuation charter and was being offered because commercial flights have been cancelled.

In a television address late Monday, Conte said Guinea was in a "state of siege" — an emergency declaration that puts the military in control of the country. He ordered the army to "take all necessary measures" to restore order and to "protect the people of Guinea from the risk of a civil war."

According to Guinean law, the emergency declaration prohibits all processions, demonstrations or gatherings and institutes a strict curfew. Guineans have been banned from appearing outdoors between 6 a.m. and 4 p.m., and between 8 p.m. and 6 a.m.

Conte said Guinea will operate under martial law until February 23.

The declaration also authorizes the military to put anyone participating in activities against the State under house arrest, gives officials wide latitude to search private property and gives the military permission to monitor phone calls and other communication.

The violence started Saturday following Conte's appointment of a close ally from his Cabinet as prime minister. Many said he sidestepped a power-sharing agreement by naming a confidant, and angry youths took to the streets, throwing stones and ransacking buildings. Security forces fired into the crowds.

The African Union issued a statement condemning the military's actions and calling for an independent inquiry.

AU Commission Chairman Alpha Oumar Konare "strongly condemns the disproportionate use of force and the repression of the civilian population, which resulted in losses of lives," the statement said.

In his broadcast, Conte said the recent days' violence represented an uprising against the State.

"I satisfactorily fulfilled all points of the demands. In spite of this goodwill, badly intentioned people restarted the union movement to ridicule the authority of the State," Conte said.

Union leaders have called for Conte's resignation and restarted a general strike Monday that they said would continue until he stepped down. Gangs of machete-wielding youths roamed the capital throughout the day, while gunfire was heard in some neighborhoods.

Residents reported hearing gunshots at the Alpha Yaya military base on Conakry's outskirts, and smoke — possibly from barricades of burning tires — rose over parts of the city. Security forces blocked roads leading into the center of Conakry, where the government is based.

At least 11 people died in Saturday's violence — most from gunshot wounds, according to medical officials and witnesses.

Sixteen more bodies of people killed in the fighting were brought to Conakry's main morgue Monday, said Hassan Bah, the director of the city's Ignace Deen hospital. It was not immediately clear when they had been killed.

Leaders of the political opposition put Saturday's death toll at more than 30 and Conakry's League of Human Rights said it had tallied 57 deaths in the interior of the country from reports by its local representatives.

No flights have landed or taken off at Conakry's airport since Saturday, an airport official said.

The president of Guinea's national assembly called for union and community leaders to return to negotiations with the government, according to a statement read on Guinea's FM Liberty radio station.

The station switched to music broadcasts from news partway through the day Monday after a raid by government forces, according to a journalist at the station.

Last month, a two-week national strike brought Guinea to an economic standstill and quickly spiraled into violence as protesters clashed with security forces. At least 59 people were killed in that unrest.

Union leaders called off the strike after Conte agreed to appoint a consensus prime minister who was not a current member of his government. The post had been left vacant since Conte fired Prime Minister Cellou Dalein Diallo in April.

Conte, who seized power in a 1984 coup, named Eugene Camara, a Cabinet member since 1997, to the post Friday. Camara served most recently as minister for presidential affairs.

Guinea's 10 million people are impoverished and many live without the most basic public services, even though the country has half the world's reserves of bauxite, a material used to produce aluminum.

Opposition leaders have also called for Conte to step down, saying the ailing president has let corruption overrun Guinea as people struggle to meet basic needs.

Conte reportedly suffers from a heart condition and diabetes, and has repeatedly traveled to Europe for treatment.