Chinese military aircraft locked their radar on Japanese fighter jets near the southern island of Okinawa, Japan's Defense Ministry said Sunday, calling it a "dangerous act."

Tokyo sent a "strong protest" to Beijing after the incidents, which resulted in no damage or casualties, Japanese Defense Minister Shinkiro Koizumi told a news conference.

Relations between the two countries have become strained after Japanese Prime Minister Sanae Takaichi suggested in November that his country could intervene militarily in the event of an attack on Taiwan.

Koizumi called the Chinese action “extremely dangerous and regrettable” and urged Beijing to prevent a recurrence.

The minister specified that “a J-15 fighter jet launched from the Chinese navy's aircraft carrier Liaoning intermittently locked its radar” on a Japan Air Self-Defense Force F-15 fighter jet that had been scrambled due to the Chinese aircraft's intrusion into Japanese airspace.

About two hours later, another Chinese J-15 intermittently locked its radar on another Japanese fighter jet, he added.

“Locking radar in these incidents constitutes a dangerous act that exceeds the scope necessary for the safe flight of the aircraft,” he noted.

Fighter jets use radar to identify attack targets, as well as for search and rescue operations.