Pope Benedict XVI has arrived in Sydney for Catholic World Youth Day celebrations.

Video: Pope Benedict XVI down under

Video: The WYD Itinerary

Video: The Papal Landing

Video: The Pontiff prepares for WYD

In depth: World Youth Day

The 81-year-old Pontiff's plane touched down at Richmond RAAF base, on Sydney's north-western outskirts, at 3pm (AEST) Sunday.

The Boeing 777 had earlier refuelled in Darwin after the 21-hour flight from Rome, and the plane reportedly circled above Dubbo, in central western NSW, to bring the last leg of his trip back to schedule.

The Alitalia plane, bearing the Australian flag and the Papal flag, taxied to the point where the Pontiff was to be met by the official welcoming party, including Sydney Archbishop, Cardinal George Pell, and Prime Minister Kevin Rudd.

Wearing his customary white robes and red shoes, Pope Benedict alighted from the plane at 3.17pm to the sound of applause.

He was welcomed with a handshake from Mr Rudd before moving along the line of dignitaries, including NSW Premier Morris Iemma.

Dr Pell kissed the Pope's hand and introduced him to other church leaders, some of whom genuflected and also kissed his hand.

Pope Benedict was then ushered inside a building at the air base, along with Dr Pell, Mr Rudd and Mr Iemma.

Meet and greet

He spent about five minutes in what was described by commentators as a "meet and greet" session with members of the clergy before joining a motorcade of white vehicles.

The Pontiff will now spend four nights at an Opus Dei-run study centre in Kenthurst before joining the official World Youth Day (WYD) program on Thursday with a spectacular "Boat-a-cade" along Sydney Harbour.

The low-key welcome ended without ceremony, with the motorcade, including police cars, ambulances, mini-buses and coaches, leaving the base just before 3.30pm.

Streets around the base were lined with up to 100 cars, whose occupants had hoped for a glimpse of the papal plane as it came in to land.

It is the Pontiff's first trip to Australia.

Official greeting to come

His official welcome to Sydney will be held on Thursday, when he will arrives on a boat on Sydney Harbour to be greeted by an estimated 500,000 people.

World Youth Day, which this year will be hosted by Sydney from July 15-20, is one of the biggest celebrations of the Catholic faith and past events have attracted more than 2 million pilgrims.

Organisers say some 100,000 overseas pilgrims have already arrived in Sydney and are among the 215,000 international and Australian Catholics who have registered for the events, which culminate in an open-air mass by Benedict.

Protesters in Melbourne

Meanwhile, about 150 protesters in Melbourne have marked the Pope's arrival in Australia with a rally against World Youth Day (WYD).

Organised by a coalition of secular groups, Youth Against World Youth Day targeted the Pope's attitude towards women, gay people, abortion, condoms and clergy sexual abuse.