Cuban soldiers fired off a 21-gun salute on Monday to mark the start of a week of memorial services for the late Fidel Castro.

Thousands of Cubans began filling Havana's Plaza de la Revolucion (Revolution Square) to commemorate Castro, carrying flowers, Cuban flags and portraits of the deceased communist leader. The square, where Castro delivered many of his most famous marathon speeches, will be the site of a two-day ceremony.

Mourners will file through a monument to national hero Jose Marti at the center of the square, walking past a black-and-white picture of Castro. The Cuban government did not say whether or not the 90-year-old former president's ashes would be on display or not.

The ceremony in Cuba's capital is expected to end on Tuesday night when foreign leaders are to pay their respects.

North Korea called for three days of mourning and said it would lower its flags to half-mast in honor of Castro.

Castro, who ruled the country for almost half a century, is admired by leftists and some in developing nations who view him as a revolutionary who stood up to the United States during the Cold War. Others, however, viewed the late leader as a dictator who oppressed Cubans and caused economic hardship that  sparked an exodus of Cubans to Florida.

Cuban authorities announced nine days of official mourning for Castro, prohibiting music and alcohol sales during the memorial period. Dissidents planned to stay home during the memorial services.

On Wednesday, a cortege will begin carrying Castro's ashes to their final resting place in the eastern city of Santiago where he launched the revolution in 1953.

Trump threatens US-Cuba 'deal'

As the memorial services in Havana got underway, US President-elect Donald Trump sent out a Tweet threatening to reverse outgoing President Barack Obama's rapprochement with Cuba.

"If Cuba is unwilling to make a better deal ... I will terminate deal," Trump said on Twitter.

In 2014, Fidel's brother and successor Raul Castro announced a diplomatic breakthrough with Obama, who has since lifted some trade barriers.

Also on Monday, the first commerical flight in over 50 years left Miami, Florida to arrive in Havana, Cuba.

(DW)