A People's Liberation Army (PLA) Navy submarine launched the missile, carrying a dummy warhead, toward international waters in the Pacific at 12.01pm on Monday, the official Xinhua news agency said.
Xinhua described the launch as a "routine arrangement" of China's annual military training and not directed against any specific country or target.
Chinese Foreign Ministry spokesperson Mao Ning said the launch was conducted "safely, in a standardised and professional manner throughout".
"We hope relevant countries will not over-interpret the matter," she said at a briefing in Beijing.
The US monitored China's test launch from a submarine of an unarmed intercontinental-range ballistic missile that landed in the southern Pacific Ocean, State Department spokesman Tommy Pigott said in a statement.
"We continue to urge China to engage in meaningful arms control discussions," Pigott said.
Xinhua did not specify what type of missile China had launched. State-controlled tabloid Global Times, citing a military expert, said it was likely to have been the JL-3, China's most advanced submarine-launched missile, which debuted at a military parade in 2025.
That missile could reach the continental United States from Chinese coastal waters, according to a Pentagon report.
"The US and others will be watching and analysing the test launch closely for any insights into PLA capability," said Meia Nouwens, a senior fellow for Chinese security and defence policy at the London-based International Institute for Strategic Studies, referring to the Chinese military.
Pacific regional powers Australia, New Zealand and Japan were given only a short period of advance notice about the test, which coincided with the signing in Fiji of a mutual defence pact between that island nation and Australia.
The test came "in the context of a rapid military buildup by China, which is lacking in the transparency and reassurance as to intent that the region expects," Australian Foreign Minister Penny Wong told reporters at a news conference in Fiji.
Mark Douglas, an analyst at New Zealand-based ship-tracking firm Starboard Maritime Intelligence, said the test would have been planned long in advance but the timing of China's notification was "interesting, to say the least".
Nouwens said China could be seeking to send a signal of its discontent about the Australia-Fiji agreement.
"That said, the launch could be counterproductive and negatively affect China's image among countries in the South Pacific," she said.
Taiwan's presidential office called the test an attempt by China to intimidate the international community.
A senior Taiwanese security official said on Monday that Taiwan was tracking an "upward trend" in Chinese naval movements during the peak military exercise season, including joint drills with Russia.
New Zealand Foreign Minister Winston Peters called the test "an unwelcome and concerning development".
"We, like our neighbours in other Pacific countries, have no interest in China using the South Pacific as a testing site for missile capability," he said.
Japan said when it was notified of the upcoming launch it had expressed "our grave concern" over the Chinese military's increased activity and urged China to reconsider.
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