ROME, April 7 (Reuters) - Pope Benedict paid tribute on Monday to Catholics and other Christians who died for their faith in Nazi camps and Soviet gulags or who were killed in hate crimes.

Benedict presided at a prayer service in a basilica on Rome's Tiber Island where the Sant' Egidio Catholic community has set up six memorials to "new martyrs".

"Stopping at these six altars, we recall Christians felled by the totalitarian violence of communism, of Nazism, those killed in America, in Asia and Oceania, in Spain and Mexico, in Africa. We are ideally re-tracing the many painful events of the past century," he said during the service.

Perhaps the most famous person whose memory is honoured at the shrine is Archbishop Oscar Arnulfo Romero, who was shot and killed by a right-wing death squad while he was saying Mass in San Salvador in 1980.

They also include a German Protestant priest who opposed the Nazis and died in Buchenwald, priests killed by Islamic extremists in Algeria and Turkey, and Orthodox Christians killed during communism in Eastern Europe. (Reporting by Philip Pullella)