In a post on X early on Sunday, Koizumi said that Tokyo has lodged a “strong protest” about the two incidents and made “a stern demand for measures to prevent recurrence”.
“The radar illumination… was a dangerous act that exceeded the range necessary for safe aircraft flight,” he added.
A fire-control radar lock is one of the most threatening acts a military aircraft can take, because it signals a potential attack, forcing the targeted aircraft to take evasive action.
In response later on Sunday, a Chinese navy spokesperson stated that a Japanese self-defence force aircraft repeatedly approached and disrupted the Chinese navy as it was training, adding that Japan’s claims were inconsistent with the facts.
The encounters over the islands, which are close to disputed territory claimed by both Japan and China, are the most serious run-ins between the two militaries in years.
They came as relations between the two countries sour over Japanese Prime Minister Sanae Takaichi declaring in November that Tokyo could respond to Chinese military action against Taiwan if the moves also threatened Japan’s security.
Democratically governed Taiwan is claimed by Beijing and lies just 110km (68.4 miles) from Japan’s westernmost Yonaguni Island.
Japan hosts the biggest overseas concentration of United States military power, including warships, aircraft and troops, with a big chunk of that contingent, including thousands of US Marines, based in Okinawa.
According to Koizumi, the Chinese J-15 jets involved in the two incidents on Saturday were launched from China’s Liaoning aircraft carrier, which was manoeuvring south of the Okinawan islands along with three missile destroyers.
“It is extremely regrettable that such incidents have occurred,” Koizumi’s statement noted.
No damage or injuries were reported from Saturday’s incidents near Okinawa, Koizumi added in his post.
The Reuters news agency, citing sources and intelligence reports, said that China deployed a large number of naval and coastguard ships across East Asian waters on Thursday. The boats at one point numbered more than 100, Reuters reported.
Taiwan’s government described that build-up as posing a threat to the Asia Pacific region. Japan announced it was monitoring Chinese activity closely.
Taiwan’s coastguard announced on Sunday that it was monitoring drills by three Chinese maritime safety ships on the western side of the Taiwan Strait’s median line, but added the situation in the waters surrounding Taiwan was currently “normal”.
Chinese state media said the search-and-rescue drills were in the central waters of the Taiwan Strait, patrolling “high-traffic areas, and areas with frequent accidents”.
Taiwan’s coastguard said China was using “misleading and false wording” about what it was doing, with the aim of harassing Taiwan and carrying out psychological warfare.
China claims it alone exercises sovereignty and jurisdiction over the strait, a major trade route for about half of global container ships. The US and Taiwan say the strait is an international waterway.
