Beijing : Beijing and Tokyo were at loggerheads Tuesday over accusations Japanese warplanes locked their fire control radar onto Chinese aircraft, as state-run Chinese media said the country needed to be ready for "military confrontation" elsewhere.
Beijing has long been embroiled in fierce territorial disputes with Tokyo over Japanese-controlled islands in the East China Sea, and with a host of littoral states over the South China Sea, which it claims almost in its entirety.
Chinese vessels and planes regularly enter waters and airspace near the East China Sea islands, called Senkaku in Japan and Diaoyu in China.
China's defence ministry late Monday accused Japanese fighter jets of using their fire control radar to lock onto two Chinese aircraft on "routine patrol" in the Air Defence Identification Zone (ADIZ) it declared unilaterally in 2013.
The aggressive move generally means an attacker is ready to fire weapons at a target.
Japan's deputy chief cabinet secretary Koichi Hagiuda denied the accusation Tuesday, telling reporters that Tokyo's Self-Defence Forces had scrambled F15 jets to monitor Chinese aircraft.
"There are no facts showing that we took provocative action against Chinese military planes," he said.
In 2013, Tokyo demanded Beijing apologise when it said a Chinese frigate had locked its fire-control radar onto a Japanese destroyer in international waters.
The row over the islands has seen relations between the world's second- and third-largest economies plunge in recent years, before recovering slightly, although they remain poor.
Beijing is also involved in a separate set of territorial disputes with other littoral neighbours over its extensive claims in the strategic and resource-rich South China Sea.
It has rapidly built up reefs and outcrops into artificial islands with facilities capable of military use.
The issue has raised tensions in the region and with the United States, which has key defence treaties with Japan and other allies in the area.
On Tuesday, China began a week of naval exercises in waters around the Paracel Islands, in the northern part of the sea.
They came a week before a United Nations-backed tribunal in The Hague rules on a case brought by the Philippines challenging China's position.
Beijing has boycotted the hearings and is engaged in a major diplomatic and publicity drive to try to delegitimise the process.
