Havana, under pressure from US President Donald Trump, had decreed two days of tribute for the men, some of whom had been assigned to Maduro's protection team.

Twenty-one of the soldiers were from the Cuban interior ministry, which oversees the intelligence services, officials have said. The others were from the military.

President Miguel Diaz-Canel and Castro, the 94-year-old retired former Cuban leader, were present in full military uniform to receive the soldiers' remains early Thursday.

Their urns, draped in Cuban flags, were unloaded from a plane at Havana's Jose Marti International Airport, according to footage broadcast on state TV.

At the event, Interior Minister General Lazaro Alberto Alvarez expressed the country's respect and gratitude for the soldiers he said had "fought to the last bullet" during US bombings and a raid by US special forces who seized Maduro and his wife from their Caracas residence on January 3.

"We do not receive them with resignation; we do so with profound pride," the minister added, and said the United States "will never be able to buy the dignity of the Cuban people."

The soldiers' bodies were then transported in Jeeps to the Ministry of the Revolutionary Armed Forces, with Cubans lining the streets and applauding the procession.

Residents of the capital can pay their respects throughout the day, which will close with a gathering outside the US embassy in Havana.

- 'Manipulation' -

The homage serves as an opportunity for Cuba to make a display of national unity at a time it is batting away pressure from US President Donald Trump.

Trump on Sunday urged Cuba to "make a deal," the nature of which he did not divulge, or face the consequences.

The Republican president, who says Washington is now effectively running Venezuela, has vowed to cut off all oil and money that Caracas had been providing to ailing Cuba.

Cuba, which is struggling through its worst economic crisis in decades, has reacted defiantly to the US threats even as it reels from the loss of a key source of economic support.

Havana has dismissed as "political manipulation" a US announcement of humanitarian aid for victims of Hurricane Melissa, which hit last October and killed nearly 60 people across the Caribbean.

"The US government is exploiting what might seem like a humanitarian gesture for opportunistic purposes and political manipulation," Cuba's foreign ministry said in a statement in response.

It added Washington had not been in touch about the delivery, which it would welcome "without conditions."

Jeremy Lewin, the senior US official for foreign assistance, on Thursday cautioned Havana not to "politicize" the help.

"We look at this as the first, the beginning of what we hope will be a much broader ability to deliver assistance directly to the Cuban people," he said.

US-Cuba relations have been tense for decades but hit a new low after the US capture of Maduro and his wife.

Twenty-three Venezuelan soldiers were also killed in the US strike that saw Maduro and his wife whisked away to stand trial in New York on drug-trafficking charges.