North Korea is once again upping the tension on the peninsula with threats of war as a series of military exercises kicked off with the Key Resolve exercise in South Korea on Monday.

Key Resolve, which will continue until March 9, involves about 2,100 U.S. personnel and about 200,000 South Korean troops. In addition, exercise Foal Eagle will be held from March 1 to April 30, during which South Korean and U.S. troops will practice land, air and marine maneuvers.

On Sunday, North Korean leader Kim Jong-un inspected four battalions of the 4th Corps, which oversaw the 2010 shelling of South Korea’s Yeonpyeong Island in the West Sea.

“Land a strong retaliatory strike on the heads of the foes if the enemy encroaches on the country’s seas where our autonomy applies by so much as 0.001 millimeter,” Kim was quoted as saying by Pyongyang’s state media Korean Central News Agency.

The North Korean leader’s comments were preceded by more direct threats from Pyongyang’s defense commission.

On Saturday, North Korea’s National Defense Commission criticized the allies’ military exercises and threatened war.

“(North Korea) will enter a holy war to bury the traitors, and domestic and foreign warmongers,” the commission said in a statement.

“Nuclear weapons are not exclusive to the U.S. We have means of war that are more powerful than the U.S.’ nuclear weapons and cutting-edge strike equipment no one else has.”

North Korea is also reported to have sent a message to South Korean authorities, saying that it was willing to engage in full scale war in response to drills in the West Sea on Feb. 20.

Pyongyang has issued such threats despite Seoul and its allies’ reassurances that the exercises are defensive in nature.

“Exercises such as Key Resolve contribute toward the ROK taking the lead for the combined defense of the Republic of Korea in 2015,” the U.S. Forces Korea said in a statement on Monday.

According to the U.S. Forces Korea, the United Nations Command Military Armistice Commission informed Pyongyang of the dates and the “non-provocative nature” of the exercise on Jan. 27.

However, with Pyongyang keeping to the custom of threatening war in response to such exercises, South Korean forces will be put on heightened alert for the duration of the Key Resolve exercise.

According to the military, reconnaissance and detection equipment including RF-4 reconnaissance aircraft, U-2 very high-altitude reconnaissance aircraft and anti-artillery radar positioned near the inter-Korean border will be in full operation until the end of the exercise.

In addition, the South Korean Air Force will place its F-15K and other fighter jets on standby.

By Choi He-suk (cheesuk@heraldcorp.com)