President Barack Obama hailed the declaration of freedom in Libya on Sunday, saying "a new era of promise" is under way in the African nation. He also urged its new leaders to turn their attention to the political transition ahead.

The leader of Libya's transitional government, Mustafa Abdul-Jalil, declared the country liberated Sunday, three days after the capture and death of dictator Moammar Gadhafi.

In a statement issued by the White House, Obama congratulated the Libyan people and said, "After four decades of brutal dictatorship and eight months of deadly conflict, the Libyan people can now celebrate their freedom and the beginning of a new era of promise."

Obama said the U.S. looks forward to working with officials as they prepare for free and fair elections.

Secretary of State Hillary Rodham Clinton said she supported calls for an investigation into Gadhafi's death as part of Libya's transition from dictatorship to democracy.

Gadhafi was captured wounded but alive in his hometown of Sirte. Bloody images of Gadhafi being taunted and beaten by his captors have raised questions about whether he was killed in crossfire, as suggested by government officials, or was executed.

Clinton told NBC's "Meet the Press" in an interview aired Sunday that she backs a proposal for the United Nations to investigate Gadhafi's death and for Libya's Transitional National Council to look into the circumstances.

Clinton said a democratic Libya should begin with the rule of law and accountability, as well as unity and reconciliation. She called investigating Gadhafi's death a part of that process.

Clinton issued a statement later Sunday congratulating Libyans on their liberation, saying the U.S. was proud to have supported "the work of ordinary, brave Libyans who demanded their freedoms and dignity."