Beijing has summoned the Japanese ambassador and Tokyo has summoned the Chinese ambassador amid an escalating dispute between the two countries over China's imposition of strict new rules on airspace over disputed waters.
The move on Monday comes after Japanese Prime Minister Shinzo Abe denounced as a "profoundly dangerous act" China's designation of an East China Sea Air Defence Identification Zone (ADIZ), which covers most of that sea and includes the skies over a group of disputed islands.
Escalatory action will only increase tensions in the region and create risks of an incident.
"Officials of the Chinese foreign ministry have summoned the Japanese ambassador to China to express China's strong dissatisfaction and solemn protest regarding Japan's unreasonable hype over China's establishing an air defence identification zone," spokesman Qin Gang told a news conference, calling the Japanese response "completely unreasonable."
The Chinese Defence Ministry also lodged formal protests Monday with the US and Japanese embassies in China after both countries criticised the ADIZ.
Tokyo, meanwhile, called in Beijing's ambassador to demand a rollback of the plan, which it said would interfere with "freedom of flight over the high seas."
China published coordinates this weekend for the newly established zone, warning Beijing would take "defensive emergency measures" against aircraft that failed to properly identify themselves in the airspace.
US Secretary of State John Kerry has called upon China to exercise caution, saying freedom of overflight was essential to stability and security in the Pacific.
"Escalatory action will only increase tensions in the region and create risks of an incident," Kerry said this weekend.
In the Japanese prime minister's first comments since Beijing unveiled the ADIZ, Abe told parliament on Monday that China should "restrain itself."
"I am strongly concerned as it is a profoundly dangerous act that may cause unintended consequences," Abe said.
China's Defence Ministry called the criticisms unfounded and irresponsible, and urged the US to stop siding with Japan.
The ministry maintained it was within the country's right to set up the zone and accused the US of making "irresponsible remarks."
"We reiterate that the purpose of China's approach is to defend national sovereignty and territorial airspace security, maintain the order of airspace flight, and is an effective exercise of our right of self defence," a spokesman, Yang Yujun, said in a statement on the ministry's website.
China confirmed the new rules would not affect "normal operations" for international flights.
Sino-Japanese relations have been strained for months because of the dispute over the tiny islands in the East China Sea, known as the Senkaku in Japan and the Diaoyu in China.
The row over the islands has festered for years, but reached a fever pitch in 2012 after Tokyo bought some of them from their private owners.
The area covered by the ADIZ also includes waters claimed by Taipei and Seoul, prompting South Korea's Defence Ministry to denounce the situation as "regrettable."