China publicly announced it had test-fired an intercontinental ballistic missile into the Pacific Ocean on Wednesday, in the first such launch in more than four decades as Beijing builds up its nuclear arsenal.

The ICBM, which was carrying a dummy warhead, “fell into expected sea areas,” the Chinese Defense Ministry said, adding that the launch “was a routine arrangement” in the military’s annual training plan.

"It is in line with international law and international practices and is not directed against any country or target," the ministry said.

Beijing had also “informed relevant countries in advance,” China’s official Xinhua News Agency said in a separate report.

But the top government spokesman in Tokyo said Wednesday that Japan had not been among those notified.

“There was no advance notification from the Chinese side to the Japanese side,” Chief Cabinet Secretary Yoshimasa Hayashi told a news conference, adding that the missile was not confirmed to have passed over Japanese territory.

NHK, citing an unidentified source, reported that the countries notified in advance included Australia and the United States.

China has in recent years ramped up the development of its missile and nuclear arsenals, the Pentagon warned in its annual report on the Chinese military last October, with Beijing developing new ICBMs “that will significantly improve its nuclear-capable missile forces and will require increased nuclear warhead production.”

"These military developments by China, combined with a lack of transparency, are a matter of serious concern for Japan and the international community,” Hayashi said.

The Chinese military’s Rocket Force has in the past made shorter-range ballistic missile training public, but ICBM launch announcements are extremely unusual, analysts said.

China’s last test-firing of ICBMs into the Pacific is believed to have taken place in May 1980, when Beijing fired multiple long-range missiles into the South Pacific, apparently in a bid to deter strikes from the Soviet Union.

While the United States regularly tests ICBMs in the area, China has been known to test-fire its longer-range weapons in its sparsely populated western Gobi Desert area.

“It is significant that this test ended in an ocean impact,” said Malcolm Davis, a senior defense analyst with the Australian Strategic Policy Institute. “Normally they test such weapons with the warheads landing in far western China.”

Further details — including what type of ICBM had been launched — were not released, but Ankit Panda, of the U.S.-based Carnegie Endowment for International Peace, suggested it may have been one of China’s most powerful missiles.

“My best guess is that this is the first Pacific Ocean test of a Chinese solid-propellant ICBM,” he said. “The best candidates would be the DF-31 or the DF-41, but we don’t know from the Chinese statement or other sources just yet.”

The DF-31 has an estimated range of 7,000 to 11,700 kilometers, while the DF-41 has an operational range of up to 15,000 km, making it China’s longest-range missile, and is reportedly capable of loading multiple independently targeted warheads.

While it was unclear where the missile splashed down, independent analysts citing Chinese NOTAMs, or notices alerting aircraft of dangers en route, said a possible trajectory could have resembled the 1980 launch, which splashed down in the center of a ring formed by the Solomon Islands, Nauru, Kiribati, Tuvalu, Western Samoa, Fiji and what is now Vanuatu.

Such a firing may have seen the missile fly over Guam, home to a sprawling U.S. military facility that would be critical in any war with China.

Guam’s Homeland Security Office of Civil Defense did not confirm whether the missile had flown over the island, but said in a statement that “no immediate threat was assessed for Guam or the Marianas from the reported launch.”

“At this point, we can probably surmise that China’s ongoing nuclear modernization may have led to a rethinking of testing requirements,” said Panda. “This may be either due to political factors, technical factors or both.”

Beijing is also due to mark the 75th anniversary of the founding of the People’s Republic of China on Oct. 1, possibly rolling out new weapons systems or advances during a large-scale military parade in Beijing.

The launch also came as Taiwan’s Defense Ministry said earlier Wednesday in a statement that it had detected recent “intensive” missile firing and other training activities by the Chinese military. The ministry said in the same statement that it had detected 23 Chinese military aircraft operating around Taiwan on “long-range missions.”

The Chinese military stepped up its activities in the region in recent weeks with repeated violations of Japanese airspace and territorial waters since late August. It also sent its Liaoning aircraft carrier between two Japanese islands near Taiwan last week.