The marines who mistakenly thought an Airbus passenger plane was a North Korean fighter jet and opened fired will not be punished, officials said on Sunday.

South Korean Marines fired rifles at a South Korean commercial aircraft flying near the sea border with North Korea, thinking it was one of the communist North's jet fighters, but they never hit their target, military sources said on Saturday.

A marine spokesman said the marines were following their training when they  shot at the airliner.

The spokesman refused to elaborate.

The shooting illustrates the level of tension between the two Koreas, still technically at war after the 1950-53 Korean conflict ended in a truce rather than a peace treaty, which came close to all-out war last year.

A Marine Corps spokesman said two soldiers guarding an island on the waters off the South's western city of Incheon fired their K-2 rifles for about 10 minutes at around 4 a.m. on Friday.

The plane was later identified as an Asiana Airlines Airbus A320 flying from China making its descent into Incheon, Seoul's main airport.

A defense ministry source said the plane, carrying 119 passengers and crew, was undamaged as it was about 500 to 600 meters out of the range of the hand-held K-2 rifles.

Asiana airlines, the operator of the aircraft, confirmed the plane was an Airbus A320 but made no other comment.

Yonhap News Agency and other local media said the soldiers believed the plane was flying north of the normal air corridor.

We checked yesterday through the air force and the airport control center to make sure there were no abnormalities such as being off course, Yonhap quoted a company official as saying.

Yonhap and other news reports quoted Marine Corps officers as saying troops would undergo thorough training on how to identify civil aircraft.

The move highlights escalated tensions between the two countries in recent memory.

Last summer the United Nations concluded that a North Korean torpedo sank the Cheonan corvette on March of 2010, killing 46 South Korean sailors.

Pyongyang has denied responsibility and said the results of the South Korean investigation were incorrect.

In November North Korea artillery fire hits South Korea island, killing soldiers and destroying homes and buildings.