A China Southern Airlines aircraft carrying 220 passengers passed through the trajectory of a rocket launched seven minutes earlier by North Korea, a South Korean official said.
Flight CZ628 was headed to Shenyang in Liaoning province after taking off from Narita airport in Japan when North Korea fired the missile at 4.17pm on Tuesday, South Korean defence ministry spokesman Kim Min-seok said.
The jet was flying over international waters at an altitude of 10,000 metres at 4.24pm when it crossed the trajectory of the missile, which reached a height of 20 kilometres, Kim said.
"The rocket could have hit the plane on its way down," Kim said. "North Korea had not given any warning. It was an unexpected and immoral act that goes against international norms."
He said the ministry had notified China through "certain channels" of the closeness of the trajectory of the missile and the passenger jet.
The North Korea missile launches coincide with joint US-South Korean military drills that the Kim Jong-un regime has denounced as a rehearsal for war. The missile launches began on February 21, disrupting a period of easing tensions between the two Koreas highlighted by the first reunions in more than three years of families divided by the 1950-1953 war.
North Korea fired seven short-range missiles into the sea yesterday, including four that the South Korean defence ministry estimated flew more than 150 kilometres, far enough to reach its capital Seoul.
The rockets hit their targeted areas off the eastern coast "precisely", the official Korean Central News Agency said, citing a North Korean military spokesman it did not identify.
In the report, the military spokesman said North Korea had the right to launch rockets in self-defence and would not abandon its nuclear deterrent for the sake of dialogue.
All North Korean troops were on "special alert" in response to the joint US-South Korean drills that began on February 24, senior South Korea defence ministry official Kim Kwang-woo said at a parliamentary defence committee hearing yesterday.
He said the North was also continuing construction at its long-range missile launch site.
Addressing the same committee in Seoul, South Korean Defence Minister Kim Kwan-jin said the North's tests were clearly meant to be provocative.
"Our military is closely monitoring for additional launches," Kim said. "It's difficult to predict North Korea's actions. I don't exclude the possibility of the North conducting additional long-range missile launches or a nuclear test," he said.
However, he said that there were no signs a nuclear test was imminent.
South Korea diverted its commercial airplanes to avoid collisions before the North launched long-range rockets in 2012. However, Kim said short-range launches like those conducted on Tuesday could not be predicted.
China's foreign ministry spokesman Qin Gang called on all sides to exercise "calm and restraint" to avoid any further escalation of tensions.
China Southern Airlines' public relations department did not respond to requests for comment on the flight yesterday.
Bloomberg, Agence France-Presse