North Korea has announced that it cannot ensure the safety of South Korean airliners flying in and around its airspace over the East Sea.

The Committee for the Peaceful Unification of the Fatherland made the announcement Friday through a statement carried by the North’s state-run Korean Central News Agency.

The committee said the North could not guarantee the safety of South Korean civilian aircraft, particularly while joint South Korea-U.S. military drills are taking place.

The annual Key Resolve-Foal Eagle military exercises open Monday and are set to last 12 days. The North denounced the drills as preparations for an invasion and a serious provocative move against its dignity and independence.

Under a bilateral memorandum of understanding, North Korea began to allow South Korean civilian airliners to pass through its airspace in 1998. The North charges 685 euros for every South Korean flight using its airspace.

After the North's announcement, two South Korean flag carriers --- Korean Air and Asiana Airlines --- ordered their flights on the Seoul-North American route to take a detour around the North's airspace starting early Friday.

In Seoul, the South Korean military speculated that the North issued the warning in a bid to have an upper hand in the general-level talks with the U.N. Command set to open on Friday at the truce village of Panmunjeom.

In Washington, State Department acting deputy spokesman Gordon Duguid told reporters that the North's latest threats are distinctly unhelpful, unwelcome and unnecessary.

He added that the North should instead be focusing on the commitments it made during the six-way nuclear negotiations.