As the sun rose over the Waitemata Harbour around 6.30am today, huge flags of the United States and New Zealand were raised over the Auckland Harbour Bridge, and then lowered to half-mast in commemoration of the terrorist attacks on the United States one year ago.

Those taking part in the ceremony included Auckland mayor John Banks, and United States Consulate General principal officer Doug Berry.

"It was a very humbling experience and very emotional on top of the harbour bridge this morning, a poignant moment," Mr Banks said afterwards.


"We were on top of the very top spans of the bridge, and I made the comment, 'I want the world to know that we here in the Southwest Pacific care, and I want the North American people to know that we honour their grief'."

It was a sad, but wonderful sight to see the Stars and Stripes at half-mast on the bridge, he said.

"Today's commemoration was a tribute to the American spirit.

"It was a beautiful, beautiful, perfectly still, clear day, looking out over the Waitemata Harbour which was a millpond and on to Auckland city which looked absolutely serene," Mr Banks said.

The floor of the New Zealand Stock Exchange was silent this morning as it delayed opening for two hours as a mark of respect.

Hundreds of finance workers were among those killed at work when two planes struck New York's World Trade Centre.

While the market was quiet other voices rose in song to mark the occasion.

At 8.46am -- the time of the attacks in New York -- New Zealand choirs opened a round-the-world 24-hour chorus of Mozart's Requiem to mark the anniversary.

The Orpheus Choir in Wellington and the Orlando Singers of Auckland performed the 45-minute requiem.

At the same time, the 51 American scientific and support staff at the South Pole's Scott-Amundsen Base joined the global effort involving an estimated 15,000 volunteers and musicians in 20 different time zones and 25 countries.

Throughout the day New Zealand emergency services vehicles are driving with their headlights on and police station flags are flying at half-mast.

At 12.30pm the nations's official remembrance service will be held at Wellington's St Pauls's Cathedral. Prime Minister Helen Clark, Governor-General Dame Silvia Cartwright and United States ambassador Charles Swindells will attend.

Before the service, Miss Clark and Mr Swindells were to plant two trees at the United States embassy. The trees -- New Zealand and American natives -- are a symbol of recovery as well as representing the two fallen towers.

Memorial church services are being held throughout most South Island centres today including Dunedin and Christchurch.

Mayor Garry Moore was speaking at a service in Christchurch Cathedral this morning.

Canterbury firefighters were attending the service and at noon they will stage their own silent parade in front of the Christchurch central fire station at noon.