The United States and France also had been pressuring the embattled president to step down after weeks of violence had gripped the impoverished Caribbean nation.
Aristide's constitutional successor, Supreme Court Chief Justice Boniface Alexandre, was sworn in later in the day and will lead the country until elections are held in 2005. In a ceremony at Prime Minister Yvon Neptune's residence, Alexandre said he "accepts responsibility with sincerity," Reuters reported.
Aristide flew from Haiti on a corporate jet at 6:45 a.m., accompanied by members of his security detail, according to a senior U.S. official. The jet carrying Aristide landed on the island Antigua for refueling and headed to South Africa, local radio stations reported.
Neptune said at a news conference that the ex-leader resigned to "prevent bloodshed."
U.S. Ambassador James Foley insisted at the news conference that the United States had not asked Aristide to resign. "President Aristide made a decision for the good of the Haitian people," Foley said. "International military forces including U.S. forces will be rapidly arriving in Haiti to begin to restore a sense of security."
The Pentagon, White House and State Department were meeting Sunday on the matter of sending military forces to try to stabilize Haiti as part of an international contingent. About 50 Marines already are in Haiti to protect the U.S. Embassy in Port-au-Prince.
In Cap-Haitien, Haiti's second-largest city in the North that has become a base for the rebels, crowds danced and sang in the street and a rebel commander said his fighters were ready to disarm once a new government was in place, according to the AP.
It was the second time that Aristide, a 50-year-old former slum priest, fled his country. Aristide was ousted in a 1991 coup, eight months after he was elected president for the first time and went into exile in the United States.
President Clinton sent 20,000 troops to restore him and end a flood of refugees to Florida but insisted Aristide respect a constitutional term limit and step down in 1995.
Aristide handpicked his successor, Rene Preval, but was considered the power behind the scenes until he won a second term in 2000, in presidential elections marred by a low turnout and an opposition boycott.
Opponents accused Aristide of breaking promises to help the poor, allowing corruption fueled by drug-trafficking and masterminding attacks on opponents by armed gangs -- charges the president denied.
The latest uprising took a violent turn Feb. 5 when rebels began taking over towns in the North, chasing away police and clashing with militant Aristide supporters. The rebels then moved south to Port-au-Prince, threatening to attack the capital if Aristide did not step down. At least 70 people have died in recent weeks.
France last week urged Aristide to resign to end the revolt, and the United States also suggested the president bow out for the good of the country.