With Covid-19 restrictions of the past two years eased, large numbers of people gathered just before the sun rose to observe solemn ceremonies, many held at beaches and war memorials in towns and cities across the two countries.

Anzac Day marks the ill-fated World War I landing of Australia and New Zealand Army Corps troops at Gallipoli, in what is now Turkey, in 1915.

Facing dug-in German-backed Ottoman forces, more than 10,000 Australian and New Zealand servicemen were killed in the Allied expedition.

Anzac Day now honours Australians and New Zealanders who have served in wars, conflicts and peacekeeping operations.

"On this particular day, as we honour those who fought for our liberty and freedom, we stand with the people of Ukraine who do the same thing at this very moment," Prime Minister Scott Morrison said as the sun rose over the Northern Territory capital of Darwin.

"Coercion travels our region once more," he added, in an allusion to China's growing political and military sway in the Pacific.

In New Zealand, Prime Minister Jacinda Ardern said the Russian invasion of Ukraine made Anzac Day especially poignant.

- 'Threat to all' -

"Fresh in all our minds is the invasion of Ukraine, a most grim reminder of the fragile nature of peace, and the devastating impact of war on people's lives," she said at a memorial service in Auckland where she laid a wreath.

"It is a threat to the international laws that a nation like ours relies on but it is also a threat to our sense of humanity," she added. "And that makes it a threat to all of us."

Earlier she attended a dawn service at Pukeahu National War Memorial Park in Wellington.

The annual commemoration comes in the run-up to May 21 elections in Australia, where the conservative coalition government is touting its defence credentials as it trails the Labor Party opposition in opinion polls.

"The only way that you can preserve peace is to prepare for war and to be strong as a country -- not to cow and not to be on bended knee and be, you know, weak," said Defence Minister Peter Dutton.

"Curling up in a ball, pretending nothing is happening, saying nothing: that is not going to be in our long-term interests," he said in an interview with Channel Nine television.

Dutton said the world was living in a period "very similar to the 1930s" with Russian President Vladimir Putin "willing to kill women and children" and China "through their actions, through their words, on a very deliberate course".

China announced last week it had signed a security pact with the Solomon Islands, raising concern in Australia and the United States that it may give Beijing a military foothold in the South Pacific less than 2,000 kilometres (1,200 miles) from Australia's coast.