Ash from Chile's volcanic eruptions prompted Australian airlines to ground some domestic services and flights to New Zealand Sunday, stranding tens of thousands of people after plumes drifted across the Pacific.

Strong winds have carried the ash clouds 9,400 kilometres (5,800 miles) across the Pacific Ocean to New Zealand since Chile's Puyehue volcano erupted more than a week ago, and they are now entering Australian airspace.

National carrier Qantas cancelled all flights to and from the southeastern island of Tasmania and all flights to and from Christchurch, Queenstown and Wellington in neighbouring New Zealand.

It later extended the groundings to all flights to and from the southern Australian city of Melbourne and those to and from New Zealand's Auckland, affecting around 30,000 passengers in total.

No intercontinental flights were immediately hit as none were scheduled to land in Melbourne on Sunday evening.

"We believe that it's absolutely the right thing to ground these services. We will put them back up in the air as soon as possible but it's a safety first approach for our customers," Qantas spokeswoman Olivia Wirth told ABC radio.

Qantas said it had taken the precautionary measure until it knew more about the density of the cloud and its possible impact on aircraft.

The Australian Associated Press (AAP) news agency said Qantas would reassess the situation early Monday.

The airline's offshoot Jetstar has also grounded flights for Tasmania and New Zealand, as well as some flights within New Zealand.

Regional rival Virgin Australia said it was suspending all domestic and international flights to and from Melbourne from Sunday, after cancelling five flights between Australia and New Zealand earlier in the day.

Air New Zealand has said it will adjust flight routes and altitudes to avoid the plumes, which New Zealand's Civil Aviation Authority has warned will be at 20,000-30,000 feet, the cruising altitude for both jet and turboprop aircraft.

The authority said Saturday New Zealand airspace might be affected for at least a week, given that the volcano was still erupting.

With thousands of passengers stranded on both sides of the Tasman Sea, Air Services Australia said the cloud had already reached Australian airspace and could affect air traffic for the next few days.

"While the main ash cloud is expected to pass to the south of the Australian mainland it has reached airspace in southern Tasmania and the south island of New Zealand," the authority said in a statement.

"The northern edge of the cloud is expected to reach Victoria, southern New South Wales and the Australian Capital Territory (Canberra), but it is also diffusing.

"This part of the ash cloud is not expected to impact south-east Australia beyond a day, but other parts of the ash cloud are being closely watched in case they move over Australia."

Andrew Tupper, head of Australia's Volcanic Ash Advisory Centre, said he expected the ash cloud to move towards Australia's east coast over the next day, although the plumes were breaking apart.

"It's got a very strong satellite signal and it's right up there with the big, big eruption clouds," he said.

"It will keep going. I would suspect it will do a loop of the globe."

Flights to and from Australia are from time to time disrupted by volcanic eruptions in the Pacific, but Tupper said this was the first time in about two decades that an ash cloud was expected to cross the continent itself.

"It's pretty major," he said.

The volcanic eruptions have already prompted the cancellation of several flights across South America.