Cuba has accused the US government of subjecting prisoners at the Guantanamo naval base to torture, cruelty and humiliating treatment comparable to abuses at Iraq's Abu Ghraib prison.
In a mounting verbal war with Washington over human rights violations, the Cuban Foreign Ministry denounced "atrocities" committed at the prison camp at the base in eastern Cuba in a diplomatic note sent to the US government.
"The arbitrary detention of these foreign prisoners without due process, as well as the tortures and degrading treatment to which they are subjected, are a gross violation of human rights and numerous international treaties and conventions," Cuba said in a statement.
Some 550 people have been held at the Guantanamo prison since the 2001 invasion of Afghanistan and other operations in the US war against terrorism.
The accusation came one day after White House national security adviser and future secretary of state Condoleezza Rice called Cuba, along with Burma, Belarus and Zimbabwe, "outposts of tyranny" that require close US attention.
Washington broke off formal diplomatic ties with Havana after President Fidel Castro's 1959 revolution, but the two countries maintain interests sections in each others' capitals.
Relations have become increasingly hostile under the Bush administration, which stepped up support for Castro's opponents and criticism of rights abuses on the island.
The four-decade-old feud flared up in December when the US diplomatic mission in Havana included among its Christmas decorations a sign with the number 75, in solidarity with 75 pro-democracy activists jailed in a 2003 crackdown on dissent.
Cuba retaliated by erecting huge billboards outside the US mission on Havana's waterfront with pictures of abused and hooded Iraqi prisoners, a swastika and the word "fascists" in bold red letters.
Cuba's communist government did not initially object to the holding of terror suspects at the US naval base at Guantanamo Bay, which it says was illegally occupied by the United States more than a century ago. But last year, Mr Castro called the prison a "concentration camp" and Cuba unsuccessfully sought United Nations condemnation.