A young German man tried to climb on to Benedict XVI's jeep on Wednesday as the pope was driving through crowds gathered in St. Peter's Square for his weekly audience.
The 27-year-old German, who was wearing a baseball cap, jumped over a wooden barricade as the pope passed by in his open-topped jeep and attempted to board the vehicle.
He was stopped by the pope's bodyguards and taken away for questioning.
He was subsequently committed to a psychiatric hospital.
The Vatican said later that the man had shown "clear signs of derangement" but had "no intention of trying to kill the pope".
"He was just trying to draw attention to himself," the Vatican said, stressing that the man had been unarmed.
But the incident brought back memories of the 1981 assassination attempt against the previous pope, John Paul II.
John Paul was shot and seriously wounded in the abdomen in the attack in the same square by Turkish national Mehmet Ali Agca on May 13, 1981. He later met Agca in prison and forgave him.
