Under Duvalier's presidency, thousands were killed and tortured, and hundreds of thousands of Haitians fled into exile, says Human Rights Watch.
A news conference at his hotel Monday was canceled at the last minute because the space was not equipped to handle the crowd, and no other location could be found, Henry Robert Sterlin, a Duvalier associate, told reporters.
Sterlin said the former dictator returned because he was moved by the anniversary of last year's tragic earthquake and because he missed his homeland.
"He's deeply hurt in his soul after the earthquake. He wanted to come back to see how is the actual Haitian situation -- of the people and of the country," Sterlin said about Duvalier.
He said he did not know how long the former leader was planning to stay.
Duvalier's arrival in Haiti coincides with an ongoing political crisis there, sparked by fraud allegations in a presidential election. A runoff vote, scheduled for January 16, was postponed after a contested first round.
His arrival brought calls for arrest from Montas and members of human rights groups.
"Duvalier's return to Haiti should be for one purpose only: to face justice," said Jose Miguel Vivanco, Americas director of Human Rights Watch. "His time to be held accountable is long overdue."
Amnesty International similarly said Duvalier should be brought to justice.
"The widespread and systematic human rights violations committed in Haiti during Duvalier's rule amount to crimes against humanity," said Javier Zuniga, special adviser at Amnesty International. "Haiti is under the obligation to prosecute him and anyone else responsible for such crimes."
The Duvalier family ruled Haiti for three decades, starting in 1957 when Francois "Papa Doc" Duvalier was elected president. He later declared himself president for life. When he died in 1971, he was succeeded by his 19-year-old son, Jean-Claude "Baby Doc" Duvalier.
The younger Duvalier held onto power for 15 years before a revolt forced him to flee the country. Widely accused of corruption, Duvalier has been living in France.
He has maintained some support in Haiti. At the offices of the National Unity Party, a few dozen of his supporters gathered around a television to listen to news reports.
"President Jean-Claude Duvalier, by coming back into the country it is a victory for Haiti," said Jean Etienne, an engineering student. "When President Jean-Claude Duvalier was in the country, it wasn't like it is now. It was better."
The former dictator was at the Karibe Hotel in Petionville, a suburb of Port-au-Prince.
Efforts to elect a new president are unfolding as the country is still struggling to rebuild after last year's devastating earthquake. Last week, Haiti marked the first anniversary of that quake, which left more than 200,000 people dead.
