Rudd demanded that the nuclear-armed country stop firing missiles immediately and return to the negotiating table, urging fellow nations to apply pressure to Pyongyang.

"This destabilising behaviour of engaging in missile firings off their own coast and the waters between themselves and Japan do nothing to contribute to regional stability, do everything to head in the reverse direction," he said.

"Our representations to the regime in Pyongyang will be robust and strong."

North Korea on Thursday test-fired four short-range missiles, according to South Korean military officials, further fuelling tension sparked by its nuclear standoff with the international community.

The missiles -- apparently surface-to-ship -- were fired into the East Sea (Sea of Japan) between 5:20 pm (0820 GMT) and 9:20 pm, defence ministry officials were quoted as saying by Yonhap news agency.

Rudd vowed to remain in "close cooperation and solidarity" with the United States, and to work with other United Nations countries to bring North Korea back to six-party disarmament talks.

"Frankly it's going to be tough but it is very important that everyone continues to apply maximum political and economic pressure on the regime in Pyongyang," he said.

The United States also condemned the missile blasts, which were the first since a new UN resolution was imposed on June 12 in response to a nuclear test in May.