The Turkish man who tried to assassinate Pope John Paul II has laid flowers at the late pontiff's tomb in the Vatican.

Mehmet Ali Agca arrived back in Rome unexpectedly and presented himself to police to declare his intention to lay the flowers.

"I felt the need to make this gesture," he told police, according to Italian media who had been tipped off in advance about his visit.

Agca's visit came exactly 31 years after John Paul visited him in prison in Rome to forgive him for the 1981 shooting that nearly killed the leader of the world's Catholics.