Jean-Claude "Baby Doc" Duvalier, who ruled Haiti from 1971 until he fled the country in 1986, has died of a heart attack aged 63.

The death of Duvalier, who returned to Haiti in 2011 after 25 years of exile, was announced by Florence Guillaume Duperval, the nation's health minister, on Saturday.

President Michel Martelly, reacting on Twitter, called him "an authentic son of Haiti" and sent his "sincere condolences to the family and to the nation".

"Love and reconciliation must always prevail over our internal quarrels. May he rest in peace," wrote Martelly, who said he was paying tribute to Duvalier "despite our quarrels and our differences."

Duvalier became the world's youngest president at the age of 19 when in 1971 he inherited power from his father, Francois "Papa Doc" Duvalier.

Like his father, Baby Doc came to rule the impoverished Caribbean nation with an iron fist, crushing opposition, clamping down on dissidents, rubber-stamping his own laws and pocketing government revenue.

Duvalier made heavy use of the dreaded Tonton Macoutes, a secret police force accused of kidnapping, torturing and killing up to 30,000 political opponents during the 1960s and 1970s.

Decades of dictatorship

An estimated 30,000 people were killed during the reign of the Duvalier father and son, rights activists say.

Despite that, reaction to his death was muted on the streets of Haiti.

The self-proclaimed "President For Life" fled for France in 1986 after riots broke out in a number of cities following his failure to address poverty and illiteracy.

Duvalier's departure ended nearly three decades of dictatorship begun by his father in 1957.

In the late 1990s, former political prisoners brought charges of "crimes against humanity" against Duvalier in a Paris court, claiming they were tortured over a period of years, but the case later foundered.

In 2007, Duvalier called on Haitians to forgive him for "mistakes" committed during his rule, even as the government in power at the time insisted he face trial.

After spending 25 years in France, Duvalier returned to his homeland in January 2011 and was briefly detained on charges of corruption, theft and misappropriation of funds.

Following his return, he took up residence in a villa in a wealthy suburb in the hills above the capital, Port-au-Prince.