Barack Obama noted the 'enormous impact of this singular figure', while Donald Trump marked the passing of a "brutal dictator"
Barack Obama says he is "extending the hand of friendship to the Cuban people" after the death of Fidel Castro.
Leaders from all over the world have been reacting to the former Cuban president's passing following a long illness.
President Obama said: "We know that this moment fills Cubans - in Cuba and in the United States - with powerful emotions, recalling the countless ways in which Fidel Castro altered the course of individual lives, families, and of the Cuban nation.
"History will record and judge the enormous impact of this singular figure on the people and world around him."
President Obama has made efforts to normalise relations between the US and Cuba during his term in office - culminating in a high-profile visit to Cuba earlier this year.
In his statement today, President Obama added: "We offer condolences to Fidel Castro's family, and our thoughts and prayers are with the Cuban people. In the days ahead, they will recall the past and also look to the future. As they do, the Cuban people must know that they have a friend and partner in the United States of America."
The US President's response stood in contrast to President-elect Donald Trump. He originally simply tweeted "Fidel Castro is dead!"
Fidel Castro is dead!— Donald J. Trump (@realDonaldTrump) November 26, 2016
In a more detailed statement released later on Saturday, Mr Trump said the world is marking "the passing of a brutal dictator who oppressed his own people for nearly six decades".
The President-elect said Castro's legacy would be "one of firing squads, theft, unimaginable suffering, poverty and the denial of fundamental human rights".
He added: "It is my hope that today marks a move away from the horrors endured for too long, and toward a future in which the wonderful Cuban people finally live in the freedom they so richly deserve.
"Though the tragedies, deaths and pain caused by Fidel Castro cannot be erased, our administration will do all it can to ensure the Cuban people can finally begin their journey toward prosperity and liberty."
People have been pouring onto the streets in Cuba and the US to lament - and celebrate - the death of the former Cuban president.
While some Cubans described his loss as "a painful blow", others rejoiced, blaming the populist leader for the deaths of innocent people and separating families.
In Old Havana, the city centre of the Cuban capital, people gathered around their radios, listening to state-run stations playing revolutionary anthems and reciting facts about Castro's life.
In Miami, Florida, jubilant Cuban exiles and their descendants chanted "Cuba si! Castro no!" on Calle Ocho - 8th Street - against the backdrop of a carnival-like atmosphere of fireworks, salsa music and car horns.
Thousands of people cheered as others drummed pots with spoons, waved Cuban flags and danced, some spraying champagne into the air.
The 90-year-old revolutionary leader's death at 10.29pm on Friday after a long battle with illness was announced on state television by his brother and current Cuban President, Raul Castro.
He said "the commander in chief of the Cuban Revolution" would be cremated on Saturday, concluding: "Until the everlasting victory, always."
Nine days of national mourning have been declared until 4 December, when Castro's ashes will be interred during a memorial service in the southeastern city of Santiago after a four-day procession through the country.
President Michael D Higgins and Foreign Affairs Minister Charlie Flanagan have released messages of condolences following the iconic and controversial leader's death.
Russian President Vladimir Putin hailed Castro as "the symbol of an era in modern world history" in a telegram to Raul Castro, adding: "Fidel Castro was a sincere and reliable friend of Russia."
Former Soviet leader Mikhail Gorbachev paid tribute to Castro for "strengthening" his island nation "during the harshest American blockade" to "a path of independent development".
French President Francois Hollande, alluding to Castro's defiance of the United States, said: "He represented, for Cubans, pride in rejecting external domination."
"Comrade Castro will live forever," said China's President Xi Jinping, while British Foreign Secretary Boris Johnson described Castro as a "historic if controversial figure", whose death "marks the end of an era for Cuba and the start of a new one for Cuba's people".
British Labour leader Jeremy Corbyn praised Castro as " a massive figure in the history of the whole planet".
Syrian leader Bashar al-Assad said: "The great leader Fidel Castro led his people's and his country's struggle against imperialism and hegemony for decades."
Pope Francis sent a message saying he was "praying to the Lord that he may rest in peace".
South African president Jacob Zuma observed: "President Castro identified with our struggle against apartheid. He inspired the Cuban people to join us in our own struggle."
Meanwhile, India's prime minister Narendra Modi said: "Fidel Castro was one of the most iconic personalities of the 20th century. India mourns the loss of a great friend."