US South Korea
US South KoreaReuters

The United States and South Korea began a joint military drill on Monday, which prompted threats from North Korea. The latter has lately received strong criticism worldwide for defying sanctions from the United Nations Security Council (UNSC) by launching several ballistic missiles. Such actions have led to tighter sanctions for North Korea by the UN.

North Korea considers the joint military drill as preparation for invasion, and has threatened a pre-emptive nuclear strike if the U.S. and South Korea continue the operation. It had also conducted a nuclear test in January, which further isolated it.  

The Ulchi Freedom Guardian exercise will continue till Sept. 2 and around 25,000 U.S. troops are expected to join it. The US-led UN Command Military Armistice Commission said that it had notified the North Korean army that the joint military drill between the two nations was not provocative.

"From this moment, the first-strike combined units of the Korean People's Army keep themselves fully ready to mount a preemptive retaliatory strike at all enemy attack groups involved in Ulji Freedom Guardian," a KPA spokesman said in a statement. 

The nuclear warmongers should bear in mind that if they show the slightest sign of aggression, it would turn the stronghold of provocation into a heap of ashes through a Korean-style preemptive nuclear strike," North's state-run KCNA news agency reported. 

It was recently announced by South Korea that the North's deputy ambassador in London had defected and arrived in Seoul along with his family. The move dealt a blow to Kim Jong Un, the leader of  the North Korean regime.

Recently even North Korea's elite group is collapsing, followed by key figures defecting to foreign countries, showing a sign of serious cracks, with chances of shaking the regime further," South Korean President Park Geun-hye said on Monday.