Shots were fired at a papal guard shortly before Pope Benedict XVI led an outdoor mass in Germany Saturday morning.
A man fired at a guard four times at the edge of the security zone about an hour before the service in the eastern city of Erfurt, Vatican and local officials said.
The pope's spokesman, the Reverend Federico Lombardi, said there was "no worry" among the papal entourage about the incident, and the pontiff was not informed about it before the mass, which was attended by 30,000 people.
"It didn't seem particularly urgent," he told reporters on the pope's plane after the Mass.
Police said the alleged shooter had been arrested and that there were no injuries.
According to the Telegraph, the man was said to have fired the shots from within an apartment before being arrested.
"Between 7 a.m. and 8 a.m., a total of four shots were fired at two members of a security firm. Neither person was hurt ... a suspect was taken into custody in an apartment. It was not the tenant of this apartment. An investigation has been launched against this person for attempted grievous bodily harm. Two airguns were secured," police spokesman Dirk Sauter said.
The service came after the pope met German victims of priest abuse in an attempt to stem the loss of support for the Catholic Church in the country.
He met Friday with two women and three men from parishes across the country, who were among the abused. The Vatican said the pope expressed "deep compassion and regret" at the suffering of those who were abused and assured them that the Catholic Church is seeking "effective measures to protect children".
Victims have accused the pope of being part of a systematic cover-up by the church hierarchy for pedophile priests in his earlier roles as an archbishop in Germany, and later when he headed the Vatican morals office.
Survivors' groups were quick to denounce the pope's meeting with victims as an empty gesture, maintaining the Catholic Church has not done enough to prosecute offending priests and prevent future abuse.
Following the mass in Erfurt, the pontiff departed for the south-western city of Freiburg, the final stop of his four-day visit.
Information from the Associated Press was used in this report.