A strict curfew kept residents inside their homes in this West African capital Tuesday after Guinea's president declared martial law, but sporadic gunfire persisted as some youths tried to renew protests that killed dozens in recent days.

Citizens were ordered inside for all but four hours in the afternoon after President Lansana Conte told the military to "take all necessary measures" to restore order. Opposition leaders and trade unions have accused Conte of violating a power-sharing agreement and demanded he step down.

At least 27 people were killed in three days of protests and clashes with security forces — most from gunshot wounds, according to medical officials and witnesses. Conakry's League of Human Rights said it had tallied at least 57 deaths in the country.

The United Nations and the African Union condemned the killing of civilians and called for an independent inquiry.

"Guinea's security forces must abide by international standards on the use of force," said Louise Arbour, the U.N. high commissioner for human rights. "The killings and violence since January ... demand an impartial investigation, as there are serious allegations of gross breaches of those standards."

Despite the curfew, residents reported hearing gunfire in the outskirts of the capital Tuesday and said some young people were trying to resume protests.

"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.

But during the curfew break, she said: "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."

Another woman in the neighborhood, Aicha Camara, said she saw trucks with helmeted troops stopping people in the streets and some soldiers firing into the air.

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

A resident of the Bambeto neighborhood said he saw soldiers force their way into a residential compound and rape two women.

"They got out and broke the door of the neighboring compound. They entered the house looking for the two women there and they raped them," said Mohammed Diallo, who said by telephone that he saw the rape from his house next door.

Another Bambeto resident, Oumar Sory Bah, said most of the area's young people had fled for fear of being arrested. Most Bambeto residents belong to the Fulani ethnic group, whereas most of the military are of the Soussou ethnicity of the ruling party.

The army ordered security forces to allow people to move about freely when the curfew is not in effect, according to state radio broadcasts. Officials said the curfew would be in effect from noon to 8 p.m. after Tuesday.

The U.S. embassy ordered all staff family members to leave Guinea and urged private U.S. citizens to go as well. The embassy flew out about 25 people on a U.S. government plane.

Conakry's airport reopened late Tuesday for an Air France flight — the first commercial plane to fly since the fighting started Saturday. A crowd of more than 2,000 people had collected at the airport over that time and witnesses said most were clamoring to get on the flight to Paris.

The violence started Saturday, a day after Conte appointed his close ally Eugene Camara, a Cabinet member since 1997, as prime minister. The post had been left vacant since Conte, who seized power in a 1984 coup, fired Prime Minister Cellou Dalein Diallo in April.

Last month, Conte agreed to appoint a consensus prime minister who was not a member of his government in a deal to end a two-week national strike that brought Guinea to an economic standstill and sparked clashes that left at least 59 dead.

Many said he sidestepped the 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. At least one radio station was raided by government forces and the U.N. World Food Program said three of its warehouses were looted.

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, used to produce aluminum.

In a television address Monday, Conte said Guinea was in a "state of siege" — an emergency declaration that puts the military in control of the country. Conte said martial law would continue through February 23.