Pope Benedict on Saturday apologised directly for the first time for sexual abuse of minors by Catholic clergy, but victims groups in Australia said they wanted action and not words.

The pope, making some of his most explicit comments on the sexual abuse scandal that has rocked the Church in several countries, also said unequivocally that those responsible should be brought to justice.

Benedict made a last-minute addition to his prepared homily in St. Mary's Cathedral, adding one powerful and personal sentence - using the word "I" three times - the Vatican had hoped would satisfy victims groups.

"Indeed, I am deeply sorry for the pain and suffering the victims have endured and I assure them that as their pastor I too share in their suffering," he said.

Acknowledging the "shame which we have all felt," he called sexual abuse of minors an "evil" and added that "those responsible for these evils must be brought to justice".

But minutes after he spoke, victims' groups said it was not enough and an anti-pope protest was held as some 250,000 young pilgrims in Sydney for World Youth Day celebrations marched to a suburban racetrack for an evening prayer vigil with the pope.

"Sorry is not enough. Victims want action, not just words," said victims' group Broken Rites, which has been pushing for an open and accountable system of investigating abuse claims. They say the Church in Australia continues to try to cover up abuse.

"A remote apology does not carry anywhere near the weight as a personal, direct apology," said Anthony Foster, whose two daughters were raped by a Melbourne priest.

"This is only an apology, it is only words, it doesn't commit all the resources of the Church to this problem ... he needs to meet with victims and victim support groups to understand what is required," Foster said.

"NO POPE" PROTEST

Around 1,000 protesters marched against Church teachings on sexual morality. Some chanted: "Pope is wrong, put a condom on," and threw condoms into the air as young pilgrims marched across the famous Sydney Harbour Bridge to the vigil site.

On pilgrim was arrested for punching an anti-pope protester in the face.

The pope confronted sexual abuse in the Church in the United States during a visit there in April, meeting victims and vowing to keep paedophiles out of the priesthood.

But his words in Australia were stronger than those he used in the United States, where the biggest of the scandals broke in 2002 and where Boston Cardinal Bernard Law resigned in disgrace that year.

Bishops in the United States and elsewhere were discovered to have moved clergy who had sexually abused minors from parish to parish instead of defrocking them or handing them to authorities.

In the United States alone, dioceses have paid more than $2 billion (1 billion pounds) to settle suits with victims, forcing some dioceses to sell off properties and declare bankruptcy.

The Catholic Church in Australia has paid millions of dollars in compensation, but has capped individual payments to tens of thousands of dollars, with many payments undisclosed due to confidentiality settlements. Victims say they are inadequate.

After praying with the pope at the vigil the crowd of young people prepared to spend the chilly night outdoors ahead of the culminating event of the celebrations - a Mass on Sunday.

The 81-year-old pope, who appears to be holding up well despite the long trip, leaves for Rome on Monday.