Japan and China launched a communication mechanism between their defense authorities on Friday to avert accidental clashes at sea and in the air, while sidestepping a territorial row over a group of small islands in the East China Sea.

"The start (of the system) is an important step to enhance the mutual understanding and trust between Japan and China," Japanese Defense Minister Itsunori Onodera said, noting that arrangements are under way to open a hotline between the countries' defense officials.

The launch of the Maritime and Aerial Communication Mechanism was a long-pending issue, with the two countries initially having agreed to set up such a system in 2007. They finally reached an agreement in May amid a recent thaw in bilateral relations that have been marred by disputes over territory and history.

Aside from the hotline, Japan and China will host in turn annual senior official and expert-level meetings to look into the operation of the system and technical problems that need to be addressed.

The two countries have also confirmed under a memorandum that the Japanese Self-Defense Forces and the Chinese military will continue to abide by existing communications protocols between vessels and aircraft to prevent an escalation of tensions.

"What we have is a contact mechanism at the level of people in the field to avoid unexpected occurrences. If the case is feared to become a major problem between the two countries, phone talks will be held swiftly between (defense) officials at an appropriate level," Onodera said at a press conference.

(A Japan Coast Guard vessel, right, chases a China Coast Guard ship in waters near the Senkakus in September 2013)

The two countries have refrained from specifying the geographical coverage of the mechanism, in an apparent attempt to avoid further complicating the dispute over the Japanese-controlled Senkaku Islands, which China claims and calls Diaoyu.

The territorial row intensified after Japan decided to bring the Senkakus under state control in 2012. Chinese government vessels have since entered Japanese territorial waters near the islets on numerous occasions.

After agreeing with Chinese Premier Li Keqiang in Tokyo to implement the mechanism, Japanese Prime Minister Shinzo Abe said in May he hopes the system will help to ease tension and build trust so "the East China Sea will become a sea of peace, cooperation and friendship."

Written notification would be required if either country decides to suspend or terminate the system.