Pope Benedict XVI knelt in the back of a flower-bedecked flatbed truck that slowly drove down a Rome boulevard in a religious procession Thursday, a day after a security scare in which a man tried to jump on his jeep in St. Peter's Square.

Benedict rode in the truck bed, beneath an open-sided canopy, as thousands of faithful walked down the street, sang hymns and held candles as part of the annual Corpus Christi procession.

Before getting aboard the truck for the half-mile procession, Benedict led a ceremony for more than an hour from atop the steps of St. John Lateran Basilica in central Rome.

The pope was accompanied in the truck by two clergymen who knelt slightly behind him. Vatican security officers on foot preceded and flanked the vehicle, and police on motorcycles kept the route open ahead.

The debate over whether the pope should be better protected in public was rekindled Wednesday after a 27-year-old German man, described by the Vatican as showing signs of "mental imbalance," jumped a security barrier and grabbed hold of Benedict's open popemobile before being tackled by security guards.

Benedict was not harmed and appeared not to have even noticed. He did not look back and kept on waving and blessing the crowd.

The man was questioned by Vatican police, then taken to a hospital for a psychiatric assessment.

"His aim was not an attempt on the pope's life, but to attract attention to himself," said the Rev. Federico Lombardi, the chief Vatican spokesman.

Security analysts said the pope exposed himself to undue risk by appearing in public at the same place and the same time each week in an open jeep.

Still, Vatican officials said they knew of no plans to increase security, writing it off as an isolated incident.

"The case is closed," Lombardi said.

The incident rekindled memories of the May 13, 1981, attempt on Pope John Paul II's life. John Paul was shot in the abdomen and seriously wounded as he was riding in St. Peter's Square in an open jeep at the start of his general audience — similar to Wednesday's scenario.

The gunman, Mehmet Ali Agca of Turkey, was caught and served his sentence in Italy before being transferred to his homeland.