A Chinese carrier strike group launched intense air operations near Japan over the weekend as the East Asian neighbours traded diplomatic barbs in an escalating dispute, further straining ties.
The encounters in waters close to Japan’s southwest island chain come after Prime Minister Sanae Takaichi warned last month that Tokyo could respond to any Chinese military action against Taiwan that also threatened Japan's security.
On the weekend, China's Liaoning aircraft carrier conducted about 100 take-offs and landings as it sailed east into the Pacific Ocean past the Okinawa Islands, Japan's Self-Defense Forces said on Monday.
Tokyo summoned China's ambassador, Wu Jianghao, on Sunday to protest behaviour it called dangerous and regrettable after the carrier's fighter jets aimed radar beams at its aircraft scrambled to shadow the vessel the previous day.
Illuminating aircraft with a radar signals a potential attack that may force targeted planes to take evasive action.
The Chinese embassy denied Tokyo's claims, saying Japanese aircraft had endangered flight safety by approaching the Liaoning as it trained with three missile-destroyer escorts.
"China solemnly demands that Japan stop smearing and slandering, strictly restrain its frontline actions, and prevent similar incidents from happening again," the embassy said in a statement.
Chief Cabinet Secretary Minoru Kihara rejected China’s claim that Japan’s aircraft had obstructed safe flight operations.
Japan will, "respond calmly but firmly and continue to monitor the movements of Chinese forces in the waters around our country," he told a regular press briefing.
A former Japanese colony, Taiwan lies just 110 kilometres (70 miles) from its westernmost island in the southwest Okinawa chain.
The US State Department and the US embassy in Tokyo did not respond to requests for comment on Japan's claims about China's use of its radar.
(Reporting by Tim Kelly and Chang-Ran Kim in Tokyo, Ben Blanchard in Taipei; Editing by Michael Perry and Clarence Fernandez)