BEIJING, March 7 (Reuters) - China has expressed its "deep concern" to North Korea after South Korea said a Chinese airplane had crossed the path of a rocket launched by the isolated state, China's foreign ministry said on Friday.
On Thursday, South Korea's defence ministry said a Chinese civilian plane had "passed as the ballistic missile (from North Korea) was in the course of descending".
The plane was flying from Toyko's Narita airport to the northeastern Chinese city of Shenyang on Tuesday, the ministry had said previously.
"On this issue, we have already contacted the North Korean side to convey our deep concern," Chinese Foreign Ministry spokesman Qin Gang told a daily news briefing.
China is North Korea's most important diplomatic and economic supporter, though Beijing's patience with Pyongyang has been severely tested following three nuclear tests and numerous bouts of saber rattling, including missile launches.
On Thursday, Qin had said the Chinese airplane was unaffected and urged Pyongyang to ensure the safety of civilian aircraft.
Media reports have identified the Chinese airplane as a China Southern Airlines flight.
A spokeswoman from the Civil Aviation Administration of China (CAACtold Reuters on Thursday that she had read the reports but had no knowledge of the incident, adding that China Southern Airlines had not contacted CAAC.
China Southern Airlines could not be reached for comment. (Reporting by Ben Blanchard and Fang Yan in BEIJING and Jack Kim in SEOUL; Writing by Sui-Lee Wee; Editing by Clarence Fernandez)