North Korea was found Tuesday to have lost 14 airmen while launching a long-range rocket in 2009, as the country's leader, Kim Jong-un, inspected a related military unit a day earlier.

Kim looked around a monument to honor the "stalwart fighters, who displayed the suicidal-attack spirit" at Unit 447 of the Air and Anti-Air Force, reported the North's official Korean Central News Agency.

The monument commemorates the "heroic feats performed by the 14 fighter pilots in the operation to ensure the successful launch of satellite Kwangmyongsong-2," said the KCNA. It did not specify how they died.

In April 2009, Kim observed the launch of the rocket, which Pyongyang claims was aimed at sending a satellite into orbit, along with his father and then-leader Kim Jong-il. The launch was unsuccessful.

Kim praised Unit 447 as the "high pride" of the country.

He said the unit also needs to play a role in leading in his campaign for forest restoration, according to the KCNA.

He planted ginkgo and other types of trees himself during his so-called field guidance at the unit on Monday, which the KCNA called a significant tree-planting day. (Yonhap)