North Korea's Kim Yo Jong, the powerful sister of leader Kim Jong Un

On Tuesday accused a US military spy plane of entering

The country's Exclusive Economic Zone eight times

State media KCNA reported

Kim warned that the US forces will face a "very critical flight"

If they continue what it called "illegal intrusion

Repeating an accusation it made on Monday

That the US had violated its airspace

By conducting surveillance flights

It also warned such flights may be shot down