Chinese warships locked their fire-control radar on a Maritime Self-Defense Force destroyer and a helicopter on two separate incidents last month in the East China Sea, prompting the government Tuesday to denounce the "very dangerous act" and lodge a formal protest with Beijing.

Defense Minister Itsunori Onodera held a hastily arranged news conference Tuesday evening to reveal the incidents, which took place on Jan. 19 and 30, saying the ministry had just finished analyzing the radar from the Chinese frigates Jiangkai I and the Jiangwei II.