Prime Minister Malcolm Turnbull has assured South Korea of Australia's solidarity in the face of threats by North Korea.
Mr Turnbull spoke on the phone on Monday night with South Korean president Moon Jae-in.
The prime minister told the president of Australia's steadfast commitment to South Korea and the pair agreed the recent nuclear test was a grave provocation.
Mr Moon thanked Mr Turnbull for his strong support and solidarity.
He also thanked the prime minister for Australia's co-operation regarding efforts to ensure tougher sanctions through a new UN Security Council resolution.
The US has called for a vote on Monday on new sanctions.
The leaders agreed effective implementation of UN sanctions by the international community was a critical part of the global effort to exert maximum pressure on North Korea to change course.
They also agreed that China and Russia had critical roles to play, not only in agreeing UNSC sanctions but in implementing them.
Mr Turnbull and Mr Moon are expected to meet face-to-face before the year's end.
North Korea was condemned for conducting its sixth nuclear test on September 3, which it said was of an advanced hydrogen bomb.
