The US missile shield caused strong backlashes from the DPRK as well as China and Russia as the THAAD's X-band radar can snoop on Chinese and Russian territories.

This year's UFG exercise would not mobilize US strategic weapons, according to local media reports, for fear of escalating the already-heightened tensions further in the region.

The DPRK slammed the UFG exercises, saying the drill is "an outrageous provocation for a nuclear war against the North aimed to encroach upon the dignity and sovereignty of the DPRK and infringe on the vital rights of its people."

The official news agency KCNA carried the statement on Sunday for the Committee for the Peaceful Reunification of the Country (CPRC) that said it is "the resolute stand of the DPRK to decisively foil all hostile acts and threat of aggression and provocation with the Korean-style nuclear deterrence."

Each year, South Korea and the United States conduct a number of joint military drills including "Key Resolve," "Foal Eagle" and "Ulchi Freedom Guardian" which they claim to be defensive in nature. But the DPRK says the annual war games are designed for northward invasion.

Seoul's unification ministry spokesman Jeong Joon-hee told a press briefing that it was very regrettable for the DPRK to distort and denounce the "annually-held defensive" exercise, urging Pyongyang to make a right choice by stopping nuclear and missile developments and avoiding provocative acts.