ISTANBUL

North Korean leader Kim Jong-un's sister said a US spy plane had breached North Korea's eastern airspace twice on Monday and warned of consequences if such illegal intrusions continue.

Kim Yo Jong said in a statement that the US is engaged in a significant military provocation through its aerial surveillance activities, the Seoul-based Yonhap News Agency reported.

She added that while North Korea will not respond directly to US reconnaissance activities outside its exclusive economic zone, any crossing of its maritime military demarcation line will result in "decisive action.”

South Korea’s military denied North Korea's claim of airspace violations, saying that flights by US aerial surveillance assets in the area are regular surveillance activities.

"We sternly urge an immediate halt to acts that create tension through such false claims," Joint Chiefs of Staff spokesperson Col. Lee Sung-jun told reporters in Seoul.