At their meeting at the Japanese Defence Ministry in Tokyo, Koizumi said, "We will respond resolutely and calmly to ensure regional peace and stability."
In the incident, a Chinese J-15 fighter jet intermittently locked its radar on the ASDF's F-15 fighter jets twice over international waters southwest of Okinawa Prefecture, southernmost Japan, on Saturday.
Marles expressed concern, stating that it is a very worrying situation.
He conveyed his intention to take joint steps with Japan.
At a joint press conference after the meeting, Koizumi emphasised, "Japan and Australia attach importance to an order based on the rule of law."
Referring to the situation surrounding Taiwan, Marles said that he does not want to change the status quo.
At the meeting, the ministers agreed to establish "the Framework for Strategic Defence Coordination," which will be headed by both defence ministers.
This framework will serve as a control tower to discuss defence cooperation in areas such as intelligence, space and cyber.
The ministers also affirmed a policy of concluding a contract by the end of this fiscal year through next March for the Australian Navy's plan to introduce an upgraded version of the Japanese Maritime Self-Defence Force's Mogami-class frigate.
On Saturday, Marles visited Mitsubishi Heavy Industries Ltd.'s Nagasaki shipyard in southwestern Japan, which builds Mogami-class frigates.
[Copyright The Jiji Press, Ltd.]