South Korean troops have fired at a passenger airliner flying from China with 119 people on board after mistaking it for a North Korean aircraft, South Korean military and aviation officials say.

Soldiers manning a guard post on Gyodong island, off the western coast of South Korea, fired their K-2 rifles towards the jet, which was descending as it approached Seoul's Incheon International Airport, the officials said on Saturday.

"The firing continued about 10 minutes but the plane was too far off the rifle's range and it did not receive any damage," the South's Yonhap news agency quoted a Marine Corps official as saying.

"When the plane appeared over Jumun island, soldiers mistook it as a North Korean military aircraft and fired."

The aircraft was flying southeast over Jumun island, 12km south of Gyodong, towards Incheon. Gyodong lies just 1.7km south of the North Korean coast.

An aviation controller told the AFP news agency that the Asiana flight from was following a normal route. Asiana is a South Korean-owned airline.

"It was flying normally. It did not deviate from its normal route," the controller said.

The incident on Friday took place close to the tense sea border between the Koreas amid heightened tensions between Seoul in the South and Pyongyang in the North.

South Korean soldiers had been alerted to possible provocative acts by North Korea amid simmering cross-border tensions.

Talking to Al Jazeera, Don Kirk, correspondent of the Christian Science Monitor newspaper in Seoul, said South Korean troops claimed the plane was so off course that they could not identify it, so they fired at it.

"They fired 99 shots, but the aircraft was not damaged as it was well out of range," he said.

"The whole episode shows just how jittery nerves are on the south coast ... [the South Koreans] have put more marines on the Yellow Sea islands and said they're going to fire back if North Korea fires at them.

"I am sure there are going to be big repercussions and concern about how you identify a plane following this incident."

Relations between the two Koreas remain at their worst point in more than 10 years after Pyongyang announced last month that it was cutting all contacts with the South's government.