Beijing said it had test-launched an intercontinental ballistic missile, firing it into the Pacific Ocean in its first such exercise in decades.

"We remain in the process of gathering further information" a spokesperson for Foreign Minister Winston Peters told AFP, saying "New Zealand views this as an unwelcome and concerning development."

"Pacific leaders have clearly articulated their expectation that we have a peaceful, stable, prosperous, and secure region," the spokesperson said.

"As part of the region, New Zealand strongly supports that expectation."

The United States and China have been vying for influence across the South Pacific -- opening embassies, inking agreements and doling out cash to Pacific island projects.

Many South Pacific nations have sought to leverage this competition for their own gain, but are keen to avoid picking sides.

The region was the crucible of the Pacific theatre during World War II and was often a test ground for US, British and French nuclear weapons.

With those memories in mind, several leaders have stressed the need to avoid the vast ocean region from being dragged into any military tussle between the world's two leading powers.

The firing of a powerful intercontinental ballistic missile will heighten those fears and startle even Beijing's allies.

"The Pacific island countries are extremely sensitive on this issue, owing to the history of nuclear testing in that part of the world" Sam Roggeveen, an expert in international security at Sydney's Lowy Institute, told AFP.

"It will be interesting to watch the scale and the tone of the response" said Roggeveen, adding that China is a "very important aid partner for most of those countries."

New Zealand has recently been pivoting towards closer ties with "traditional allies" in Britain and the United States, despite deep economic dependence on trade with China.

Wellington said it had "engaged Pacific partners, and we will continue to do so in the coming days."