More than 6000 Catholic pilgrims have descended upon the city streets for Brisbane's own mini-World Youth Day, ahead of the main event in Sydney this week.

The pilgrims from more than 40 countries, waving flags and banners, can be heard singing national songs as they march.

Shouts from the Australian contingent could be heard above most.

"Aussie, Aussie, Aussie - Oi, Oi, Oi!"

Bongo drums from the Congo are leading the Brisbane diocese, alongside East Timorese pilgrims, whose chanting resounded down Adelaide Street.

They departed from five inner-city churches this morning, where they were officially welcomed to the Sunshine State ahead of Brisbane's festival called Heart of the City at Roma Street Parklands.

It was a rare sight inside St Stephen's Catholic Cathedral on Elizabeth Street, where the congregation partook in a mass Mexican wave.

Brisbane families and parishes will host 5000 pilgrims from more than 40 countries over the weekend.

One of the biggest groups, comprising 800 pilgrims, is staying at Nudgee College, Boondall, on Brisbane's northside.

Event organiser Issac Moody said Brisbane's mini-World Youth Day would show off the city's Christian and Catholic communities.

Along with Brisbane's international guests, more than 3000 pilgrims from southeast Queensland will board buses, trains and planes to Sydney from tomorrow - on route to the world's largest international gathering of Catholic youth.

The highlight of the week-long Catholic gathering will be an open-air Mass with Pope Benedict at Randwick Racecourse on July 20, which is expected to attract 500,000 people.

Today's celebrations in Brisbane will culminate in the city's parklands, where the multi-cultural fiesta of song and dance will continue.