North Korea announced nuclear threats against the United States if it does not end its ongoing military exercises with South Korea. Pyongyang said it will not hesitate to use its latest weapons that are "unknown to the world."

The annual military exercises will commence on Monday, which will involve the United States, South Korea and other allies. Ulchi Freedom Guardian, the proper title of the exercises, aims to "protect the region and maintain stability on the Korean peninsula," said the Korea-U.S. Combined Forces Command, according to CNN.

The annual event consistently receives threats from the North Korean government.

 "The further Ulchi Freedom Guardian joint military exercises are intensified, the strongest military counteraction the (Democratic People's Republic of Korea) will take to cope with them," said a North Korea National Defense Commission's (NDC) spokesperson. "The army and people of the Democratic People's Republic of Korea (DPRK) are no longer what they used to be in the past when they had to counter the US nukes with rifles."

This threat was announced a day after North Korea said it will turn the South into a "sea of fire" if activists from South Korea continue their campaign. Activists try to send across the border leaflets through helium balloons, Agence France-Presse reported. North Korea added that the attacks will be "indiscriminate strikes which envisage even possible challenge and escalating counteraction."

Aside from nuclear threats, North Korea said it will attack Washington on U.S. soil, according to the Economic Times.

"If US wants their mainland to be safe," said a news reporter from Korean Central News Agency, "then the Ulchi Freedom Guardian should stop immediately."