South Korea and the U.S. have begun a massive joint military exercise amidst threats by North Korea that they may launch a sacred war using nuclear equipment against them.

The annual military exercise, known as Key Resolve, will involve around 200,000 South Korean and 2,100 U.S. troops in what officials from both countries have stressed is a routine training exercise.

The news comes after Pyongyang threatened to launch a war against the South last Saturday, calling the allies warmongers.

According to the North's Korean Central News Agency (KCNA), The war drills are an unpardonable infringement upon the sovereignty and dignity of the [Democratc People's Republic of Korea] as they evidently target the DPRK, which is in the mourning period.

Hundreds of thousands of [North Korean] troops are poised for a war carrying nuclear war equipment.

The army and people of the DPRK are fully ready to fight a war with them, the agency added.

Military personnel from Australia, Canada, Denmark, Norway and the U.K. will also take part in Key resolve, which will go on until March 9.

In response to the exercise, North Korea's new leader Kim Jong-Un inspected frontline artillery units Sunday, the Korea Times reported.

The paper added that the North had placed its 4th Army Corps, stationed near the border, on heightened alert after earlier conducting live fire drills allegedly targeting the South.