LONDON — Pope Benedict XVI said today he was ashamed of the "unspeakable" sexual abuse of children by priests, telling the British faithful during Mass in Westminster Cathedral that he was deeply sorry and hoped the church's humiliation would help victims heal.

Benedict also said he hoped the church would be able to use its contrition to purify itself of the "sins" of its ministers and renew its commitment to educating the young.

Benedict addressed the abuse scandal head-on during his homily, which was broadcast live on British television, a day after six people were arrested in an alleged terrorist plot against him. They remained in custody Saturday.

The sex abuse scandal has clouded Benedict's four-day state visit to this deeply secular nation with a centuries-old history of anti-Catholic sentiment. Polls have indicated widespread dissatisfaction in Britain with the way Benedict has handled the crisis, with Catholics nearly as critical of him as the rest of the population.

Anger over the abuse scandal runs high in Britain in part because of the enormous scale of the abuse in neighboring Ireland, where government reports have detailed systematic abuse of children at church-run schools and cover-up on the part of church authorities.