Defence has confirmed that five Australian soldiers have been killed in two separate incidents in Afghanistan.

Three Australian soldiers were killed by a man in an Afghan army uniform in a 'green on blue' attack at a base in Uruzgan province in the south of the country yesterday.

Two other Australian soldiers were wounded in that incident.

In a separate incident early this morning, two special forces soldiers were also killed when their chopper crashed in the Helmand province.

Prime Minister Julia Gillard said that in a war of so many losses, this was Australia's single worst day in Afghanistan and "the most losses in combat since the days of the Vietnam War".

Here is how the news was broken to the nation and how its leaders and military experts reacted.

9:10pm: The head of NATO issued his condolences to the Australian people.
"Our thoughts are with the loved ones of those killed and wounded in Afghanistan, and with the Australian people," Brussels-based secretary-general Anders Fogh Rasmussen said on Twitter.

The Dane said he had spoken to Australia's NATO ambassador earlier in the day "to express my condolences for the tragic loss Australia suffered in the last 24 hours."

He added: "Australia's response to these tragic events in Afghanistan is exemplary. Australia is a strong and steadfast NATO partner."

As it happened: Five Aussie soldiers killed in Afghanistan - ABC News (Australian Broadcasting Corporation)