China's Foreign Ministry spokesman Qin Gang criticised Ashton's remarks, saying China hoped the EU could treat the situation "objectively and rationally".
"Actually, Madam Ashton should know that some European countries also have air defence identification zones," Qin said. "I don't know if this leads to tensions in the European regional situation. European countries can have air defence identification zones. Why can't China?"
Asked to clarify China's expectations for what information airlines were expected to report, Qin said: "International law does not have clear rules on what kind of flight or airplane should apply", adding that each country made its own rules.
"Therefore, China's method does not violate international law and accords with international practice," he said.
China's Foreign Ministry said on Thursday that since the zone had come into force there had been no impact on the safe operation of international civilian flights, although it added that China "hoped" airlines would cooperate.
Japan's two biggest airlines have defied the identification order since Wednesday at the request of the Japanese government.
Although there are risks of a confrontation in the zone, U.S. and Chinese military officials have stepped up communication with each other in recent years and are in regular contact to avoid accidental clashes.
U.S. Vice President Joe Biden is visiting China, Japan and South Korea next week, and will try to ease tensions over the issue, senior U.S. officials said.
"We decline to comment on Chinese flights, but the United States will continue to partner with our allies and operate in the area as normal," a Pentagon spokesman said.
China's Defence Ministry has said that it was aware of the U.S., Japanese and South Korean military aircraft in the zone and had tracked them all.
Ties between China and Japan, often tense, have increasingly been frayed in recent years by regional rivalry, mutual mistrust over military intentions and what China feels is Japan's lack of contrition over its brutal occupation of parts of China before and during World War Two.
In a show of support for the military, Chinese President Xi Jinping visited a base in Jinan in eastern China, where he said "military training is critical to beef up the PLA's (People's Liberation Army) war capacities", according to the Xinhau news agency.
Xi did not make direct mention of the East China Sea air defence zone.
"Though life is becoming better, history can't be forgotten and those who made sacrifices for (the) new China's founding must be remembered," Xinhua quoted Xi as saying in a separate report.
The Global Times, an influential tabloid published by the ruling Communist Party's official People's Daily newspaper, praised the government for its calm response in the face of "provocations", saying China would not target the United States in the zone as long as it "does not go too far".
But it warned Japan it could expect a robust response if it continued to fly military aircraft in the zone.
"If the trend continues, there will likely be frictions and confrontations and even a collision in the air ... It is therefore an urgent task for China to further train its air force to make full preparation for potential conflicts," it wrote in an editorial on Friday.