Kim Yo-jong, the powerful sister of North Korean leader Kim Jong-un, on Monday claimed US reconnaissance aircraft intruded in the country's airspace.

Kim issued a statement alleging that a US spy aircraft intruded in the North's eastern airspace twice at around 5 a.m. and 8:50 a.m., respectively, on the same day.

In a statement carried by the Korean Central News Agency, she said the US is "engaging in a serious military provocation by conducting aerial surveillance."

Kim Yo-jong added that the North will not respond directly to the US reconnaissance activities outside of the country's exclusive economic zone, but warned that it will take "decisive action" if the US military again crosses its maritime military demarcation line.

Meanwhile, South Korea's military rejected the North's claim of its airspace being violated as "not true" and described flights by US aerial surveillance assets around the peninsula as part of 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. (Yonhap)