Story highlights The message was delivered over the phone in English, reports say

Such threat happen routinely before U.S.-South Korean exercises

The exercises come in the wake of a recent nuclear test in North Korea

South Korea's military is already in a state of heightened alert

Ahead of annual, routine military exercises between South Korea and the United States, North Korea issued its usual caustic objections Saturday.

It threatened "miserable destruction," if "your side ignites a war of aggression by staging the reckless joint military exercises ... at this dangerous time."

Though customary, the stark posturing by North Korea stands in the shadow of an underground nuclear test two weeks ago that was preceded by the launch of a long-range missile capable of transporting a warhead.

The detonation of the nuclear charge was the third in Pyongyang's history and the first under supreme leader Kim Jong Un's rule. South Korea's military reacted with fierce military drills, including a public display of newly deployed cruise missiles with pinpoint accuracy.

It has been on heightened readiness ever since.

The test also triggered a global wave of condemnation, including from Beijing, and plans for new sanctions against Pyongyang.

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North Korea issued the objections to exercises Key Resolve and Foal Eagle scheduled for March and April to U.S. commander James D. Sherman, state run news agency KCNA reported.

The message was delivered over the phone in English, South Korean news agency Yonhap reported.

It also condemned the threat of new sanctions over North Korea's recent actions.

A United Nations military commission informed Pyongyang of the upcoming routine exercises, according to a joint statement from U.S. and South Korean military officials.

The commission also told North Korea that they are "not related with the current situations on the Korean Peninsula."

Around 10,000 U.S. forces will participate in Foal Eagle from March 1 to April 30. Key Resolve will involve 10,000 South Korean troops and 3,500 U.S. troops in exercises March 11 to 21.

Key Resolve will include U.N. troops and neutral supervisors.