Pope Benedict XVI said on Saturday he was deeply ashamed of the "unspeakable" sexual abuse of children by priests, telling the British faithful during Mass in Westminster Cathedral that he hoped the church's humiliation would help victims heal. Benedict also said he hoped that the church would be able to use its contrition to purify itself from the "sins" of its ministers and be able to renew its commitment to educating the young. Benedict confronted the abuse scandal head-on during his homily, a day after six people were arrested in an alleged terrorist plot against him. They remained in custody on 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. The pontiff issued his comments in the seat of British Catholicism amid speculation that he might meet with British abuse victims, and as abuse survivors and others opposed to his visit prepared a march on Saturday afternoon in London's Hyde Park to demand more accountability. "I express my deep sorrow to the innocent victims of these unspeakable crimes, along with my hope that the power of Christ's grace, his sacrifice of reconciliation, will bring deep healing and peace to their lives," Benedict said. He said he acknowledged the shame and humiliation all the faithful had suffered as a result of the sins and said he hoped "this chastisement will contribute to the healing of the victims, the purification of the church and the renewal of her age-old commitment to the education and care of young people." On his way to Britain, Benedict acknowledged to reporters that the church had failed to act quickly or decisively enough to stop the abuse and prevent it from recurring. Victims groups have dismissed such comments as hollow, saying they want the church to turn over information it has about suspected pedophiles in its ranks.