Ailing Cuban leader Fidel Castro took on front-running U.S. Republican presidential candidate John McCain on Monday, accusing him of lying about Cubans torturing American prisoners of war in Vietnam.

At a campaign stop in Miami last month, the Arizona senator told anti-Castro exiles that American POWs held with him in Hanoi were tortured by "a couple of Cubans."

"His accusation against the Cuban revolutionaries ... are completely unethical," Castro wrote in an article published by the ruling Communist Party newspaper Granma.

"The commandments of the religion you practice prohibit lying," he said of McCain, who was raised an Episcopalian and calls himself a Christian....

Castro's criticism brought a sharp retort from McCain as he campaigned in Annapolis, Maryland.

"For me to respond to Fidel Castro, who has oppressed and repressed his people and who is one of the most brutal dictators on Earth, for me to dignify any comments he might make is certainly beneath me," he said at a press conference....

Castro said the Vietnam War ended in a disastrous withdrawal by the United States.

"All they achieved was a candidate for the Republican Party 41 years later," he wrote.