VATICAN CITY — A German man jumped a security barrier and grabbed hold of Pope Benedict XVI’s open popemobile before being tackled by security guards yesterday — reviving a debate over whether the pontiff should be better protected during his public audiences.Benedict was not harmed and appeared not to have even noticed: He did not look back and kept on waving and blessing the crowd in St. Peter’s Square. But security analysts said he exposes himself to undue risk by appearing in public at the same place and the same time each week in an open jeep.

“If he cannot change the route or the hour, he must use at least a protected car,” said Claude Moniquet, head of the European Strategic Intelligence and Security Center, a Brussels-based think tank on security issues.

In yesterday’s incident, the man vaulted himself up and over the wooden barrier in St. Peter’s Square in an apparent attempt to jump into the white popemobile. He managed to grab onto the back of the vehicle before about eight security guards who were trailing the car tackled him and pinned him to the ground.

Without flinching, the German-born pope kept on waving and blessing the crowd. The jeep kept moving slowly forward, and the audience proceeded as if nothing had happened.

The Vatican spokesman, the Rev. Federico Lombardi, identified the man only as a 27-year-old German who showed signs of “mental imbalance.” The man was questioned by Vatican police, before being taken to a hospital for psychiatric assessment.

“His aim was not an attempt on the pope’s life, but to attract attention to himself,” 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 — a similar scenario to that of Wednesday.

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

Moniquet, the security expert who has written about protecting heads of state, said leaders such as the pope must balance proximity to the public with their own security requirements. But unlike other world leaders who make occasional forays into the public domain, the pope has a regular appointment with the faithful each Wednesday morning — precisely the type of routine that security guards try to avoid.

“The fact is you cannot ensure 100 percent protection,” he said. “It’s around the Vatican. It’s a ritual. I’m afraid there are not a lot of options” other than an armoured car.

Nevertheless, Vatican officials said yesterday there were no plans to change the long-standing use of open vehicles for the audience inside the Vatican.

When the pope travels abroad, he uses a popemobile outfitted with bullet-proof glass.

Moniquet noted that people go to papal audiences to see the pope — something that bulletproof glass would still permit. However, such protection would prevent the pontiff from blessing babies that are occasionally passed up to him by his guards, as he did on Wednesday.

Since the September 11, 2001, attacks, the Vatican has tightened security in St. Peter’s Square when the pope is present. All visitors must pass by police to get into the square, with some going through metal detectors or being frisked by metal detecting wands.

Nevertheless, virtually anyone can attend. Tickets can often be obtained at the last minute — particularly in good weather when the audience is held outside in the piazza.

St. Peter’s is cordoned off with wooden barricades to create “routes” that the popemobile can drive along to make the pope more visible to the crowd, which on Wednesday numbered some 35,000.

The pope is protected by a combination of Swiss Guards, Vatican police and Italian police.