Japan has condemned a reported violation of its airspace by a Chinese military aircraft as “utterly unacceptable” and a threat to its security.

The incursion, described by Japanese media as the first of its kind by a Chinese military plane, comes after repeated maritime provocations by Chinese vessels near disputed islands in the East China Sea in an escalation of regional tensions.

The incursion was a “serious violation of sovereignty”, Japan’s chief government spokesperson said on Tuesday. “The violation of our airspace by Chinese military aircraft is not only a serious violation of our sovereignty but also a threat to our security and is totally unacceptable,” Yoshimasa Hayashi told reporters.

He added: “We understand that this is the first confirmed and announced airspace incursion by a Chinese military aircraft since we started the anti-airspace incursion measures.

“We refrain from giving a definite answer as to the intended purpose of the Chinese aircraft’s action. However, China’s recent military activities near Japan have a tendency to expand and become increasingly active.

“The government will continue to pay close attention to China’s military activities and will take all possible measures to ensure vigilant surveillance and airspace violation measures.”

A Y-9 surveillance aircraft breached Japanese airspace for about two minutes from 11.29am on Monday, Japan’s defence ministry said.

The ministry said the aircraft “violated the territorial airspace off the Danjo islands in Nagasaki prefecture”, prompting Japan to scramble “fighter jets on an emergency basis”.

It said “warnings” and other steps had been issued to the aircraft, but public broadcaster NHK reported that no weapons, such as flare guns, had been used.

The defence ministry released a photograph of what it said was the plane, which reportedly circled above waters southeast of the islands multiple times before and after entering Japan’s airspace, Kyodo news agency said. It headed back towards China at about 1:15 pm.

The deputy foreign minister, Masataka Okano, summoned China’s acting ambassador late on Monday to lodge a “firm protest”, and called for measures against a recurrence, the foreign ministry said in a statement.

The Chinese diplomat said in response that the matter would be reported to Beijing, the ministry said. There was no immediate official comment from Beijing.

A Japanese defence ministry source told Kyodo that China “might be trying to provoke a reaction from Japan,” while an unnamed government official said the aircraft had “merely grazed” Japan’s airspace, possibly after straying off course.

Two previous incursions were by non-military aircraft, Japanese public broadcaster NHK reported. A propeller-powered plane and a small drone went into airspace near the disputed Senkaku islands in 2012 and 2017.

Chinese vessels regularly enter waters near the Senkakus, with Japan scrambling self-defence force jets in response. The uninhabited islands, surrounded by rich fishing grounds and potential oil and gas deposits, are administered by Japan but claimed by China, where they are known as Diaoyu.

The territories were in the news again recently after the Japanese coastguard rescued a Mexican man who had become stranded on one of the islands after leaving the island of Yonaguni in a canoe in an apparent attempt to cross to Taiwan, 100km away.

Yee Kuang Heng, a professor at the University of Tokyo, said the Y-9 in Monday’s incident “was likely probing Japan’s air defence network, collecting electronic intel such as Japan’s radar signals and coverage”.

China’s growing economic and military clout in the Asia-Pacific region and its assertiveness in territorial disputes – in particular with Taiwan – has alarmed the United States and its allies.

Japan, whose defence forces are constricted by the country’s postwar “pacifist” constitution, has ramped up defence spending with US encouragement, moving to acquire “counterstrike” capabilities and easing rules on arms exports.

Tokyo is also providing funding and equipment such as patrol vessels to countries across the region and agreed in July on a deal with the Philippines allowing troop deployments on each other’s soil.

Japan and South Korea have also moved to put historical tensions behind them. Tokyo is part of the Quad alliance with the US, Australia and India, a grouping seen as a bulwark against Beijing.

The remote Senkaku chain has fuelled diplomatic tensions and been the scene of confrontations between Japanese coastguard vessels and Chinese fishing boats. Tokyo has reported the presence of Chinese coastguard vessels, a naval ship and even a nuclear-powered submarine, in the area.

The Danjo Islands, the site of the latest incident, are a group of small islets also located in the East China Sea off Japan’s southern Nagasaki prefecture.

Beijing also claims the South China Sea almost in its entirety.

The incident with Japan came as the Philippines’ defence minister, Gilberto Teodoro, called China the biggest disruptor of international peace in the region.

Speaking at an annual military conference of the US Indo-Pacific command, Teodoro urged partner nations to call out China’s “illegal actions” in the South China Sea.

China rejects a 2016 ruling by the permanent court of arbitration in The Hague that Beijing’s expansive claims over the South China Sea has no basis under international law.

US national security adviser Jake Sullivan is due to visit Beijing for three days from Tuesday and will meet China’s foreign minister, Wang Yi, in a bid to manage bilateral tensions ahead of the US presidential election in November.

With Agence France-Presse and Reuters