Havana, Cuba: Throngs of Cubans began streaming to Havana's iconic Revolution Square to pay tribute to Fidel Castro on Monday, kicking off an emotional, week-long farewell to the divisive Cold War titan.

Mourners, many of whom had lined up before dawn, began filling the square as soon as it opened with a salvo of 21 cannon shots from a colonial fort overlooking Havana harbor.

They filed past a black-and-white picture of "El Comandante" as a young revolutionary, many clutching bouquets of flowers, many others in tears.

"I got here at 6:00 pm yesterday. I don't know what to say," said Josefina Vayan Bravo, a 44-year-old housewife, before breaking into sobs.

Castro, whose 1959 revolution toppled a dictatorship with the promise of bringing justice and equality to his Caribbean island, was a towering figure of the 20th century.

While some saw him as a socialist hero who brought education and free health care to this country, others labeled him a "dictator" who caused economic hardship and sparked an exodus of Cubans to Florida seeking a better life.

Hundreds of thousands of people are expected to swarm Revolution Square, where Castro would often rail against the US "empire" during his legendary, marathon speeches.

Many mourners were dressed in state uniforms -- school children, soldiers, veterans, doctors and customs officers.

Lourdes Rivera, a 66-year-old retired civil servant, was so overcome with emotion she sat on a curb and cried.

"He's the father of all Cubans. My dad was my dad, but he couldn't give me what (Castro) gave me. He gave me everything. My freedom. My dignity," she said.

"There will never be another like him," said 84-year-old Teresa Oquendo between sobs.

- Terminator Trump? -

In a sign of changing times, US President Barack Obama visited Revolution Square during his historic visit to Havana in March, when he became the first US leader since 1928 to step foot in Cuba.

In 2014, Fidel's brother and successor, Raul Castro, announced a diplomatic detente with Obama, who has lifted some trade barriers. On Monday, the first regular flights from the United States to the Cuban capital will resume.

But US President-elect Donald Trump threatened Monday to end the thaw unless Havana makes concessions on human rights and opening up its economy.

"If Cuba is unwilling to make a better deal for the Cuban people, the Cuban/American people and the US as a whole, I will terminate deal," he said on Twitter.

Raul Castro has enacted modest, slow reforms that have slightly opened up the economy. Government opponents hope that Fidel's death will prompt him to launch bolder changes.

Fidel handed power to Raul Castro in 2006 after undergoing emergency intestinal surgery. His cause of death on Friday at age 90 has not been disclosed.

- 'Nothing changes' -

Authorities had initially said Castro's ashes would be displayed in an urn, but there was no sign of it as the memorial began.

There was a visible police presence inside and around Revolution Square.

Dissidents who were repressed by Castro's regime for years said they were happy that the "dictator" had died, but they called off regular demonstrations on Sunday out of deference to those in mourning.

In Miami, where so many flocked in the past decades, Cuban-Americans celebrated the death of the man they called a "tyrant" with street parties throughout the weekend.

After two days of commemorations in the capital, Castro's ashes will go on a four-day island-wide procession starting Wednesday before being buried in the southeastern city of Santiago de Cuba on December 4.

Santiago, Cuba's second city, was the scene of Castro's ill-fated first attempt at revolution in 1953 -- six years before he succeeded in ousting the US-backed dictator Fulgencio Batista.

Castro, who came to power as a bearded, cigar-chomping 32-year-old, adopted the slogan "socialism or death" and kept his faith to the end.

He survived more than 600 assassination attempts, according to aides, as well as the failed 1961 US-backed Bay of Pigs invasion.

His outrage over that botched attack contributed to the Cuban missile crisis the following year, when the US discovered Soviet missiles on island just off its coast -- pushing the world to the brink of nuclear war.

Daniel Martinez, a 33-year-old cook, is not a fan of the regime but was not thrilled with the celebrations in Miami either.

"I have nothing personal against Fidel, but I am not a 'Castrista.' I don't consider myself a dissident. I simply don't like this system," he said. "Nothing changes here. Nothing moves."