SYDNEY, Australia - A massive Catholic youth celebration kicked off Tuesday with an Australian "G'Day" and a welcoming text message from Pope Benedict XVI to the tens of thousands of pilgrims who have traveled here from around the world.

As the clock struck midnight, a giant countdown clock ticked over to read "G'Day Pilgrims" -- Good Day Pilgrims -- drawing wild cheers from flag-waving youth who had gathered at St. Mary's Cathedral to mark the start of the six-day celebration.

Registered pilgrims received the first of daily inspirational text messages from the pope.

Organizers say nearly 250,000 people have registered for World Youth Day, more than half of them from overseas.

The pope, who arrived Sunday, is resting at a secluded retreat on the outskirts of Sydney until Thursday, when he starts a busy round of meetings, takes a cruise on Sydney Harbour and makes a major address to the pilgrims. The festival culminates with a papal Mass on Sunday.

Also Tuesday, a federal court struck down a new law that banned people from annoying pilgrims, ruling that it restricted free speech.

The ruling cleared the way for the NoPope Coalition -- a group of gay rights and secular activists opposed to the pope's policies on contraception, abortion and homosexuality _ to hand out condoms and coat hangers -- symbolizing abortions -- to pilgrims at a Saturday demonstration.

Jess Sudholz, a teenage pilgrim from the Australian state of Victoria, was unfazed by the prospect of protests.

"I think everyone should be allowed to say what they want. It's their opinion,'' Sudholz said. "We're still going to have fun.''

Benedict has raised expectations that he will apologize directly to victims of past clergy sexual abuse while in Australia, telling reporters he will do everything possible to achieve "healing and reconciliation with the victims.'' Activists in Australia have demanded a formal apology from the pope.

Sydney Archbishop Cardinal George Pell, who met briefly with Benedict on Monday, said the church in Australia had apologized to clergy abuse victims a number of times, and was still struggling to help them heal. "That's the most important thing. Counseling, help, justice,'' Pell said.

Benedict also signaled he will discuss the need to face up to the "great challenge'' of caring for the environment, noting that global warming is an issue worrying many young people.

There was a minor security scare at Benedict's retreat late Monday, when a police officer in a guard unit accidentally set off what authorities described as a "distraction device,'' seriously burning his hands. Deputy Police Commissioner Dave Owens said the pope was never in any danger.