The incident occurred aboard the national carrier's daily flight from the eastern Chinese city of Hangzhou to Incheon International Airport, near Seoul, South Korea.

"A lithium battery spontaneously ignited in a passenger's carry-on luggage stored in the overhead bin on flight CA139," the airline said in a statement on Chinese social media platform Weibo.

"The crew immediately handled the situation according to procedures, and no one was injured," the statement said.

The plane was diverted for an unscheduled landing at Shanghai Pudong International Airport "to ensure flight safety", it added.

Bright flames were seen coming from an overhead storage compartment in an image taken by a passenger and published by state-affiliated domestic media outlet Jimu News.

There was black smoke in the cabin, the image showed, as at least one passenger was seen trying to extinguish the blaze.

Data from tracking website Flightradar24 showed that the flight took off from Hangzhou at 9:47am local time.

It made a complete turn over the sea roughly equidistant from the eastern Chinese coast and Japan's southern island of Kyushu, landing in Shanghai shortly after 11am local time.