Annual military exercises come amid a festering rift between the two Koreas

Republic of Korea and US forces kicked off their joint annual war games on Monday despite strong backlash from the Democratic People's Republic of Korea.

The Ulchi Freedom Guardian will be conducted from Aug 22 to Sept 2, said Combined Forces Command in a news release.

The computer-assisted simulation exercise will mobilize about 25,000 US troops, including 2,500 reinforcements from the US mainland and the US Pacific Command. It's lower than last year's 30,000 US forces.

From the ROK side, some 50,000 forces will join the military exercise. It was almost the same as last year's.

The combined forces will reportedly apply Operation Plan 5015 to this year's UFG exercise. The OPLAN 5015 is a wartime joint defense scenario signed in June 2015 between Seoul and Washington to pre-emptively destroy the DPRK's nuclear and missile bases in times of military conflicts.

The United Nations Command's military armistice commission notified the DPRK at about 9:40 am local time of the drill schedule and its defense nature verbally in Panmunjom, the truce village in the border dividing the two Koreas.

All military communications lines between the ROK and the DPRK have been shut down after Pyongyang's nuclear detonation in January and its launch of long-range rocket in February that was seen as a disguised test of ballistic missile technology.

Tensions were heightened further as Seoul and Washington agreed in July to deploy one Terminal High Altitude Area Defense or THAAD battery on ROK soil by the end of next year.

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 in the region.

The DPRK slammed the UFG exercises, saying the drill is "an outrageous provocation for a nuclear war against the DPRK aimed at encroaching on the dignity and sovereignty of the DPRK and infringing 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 that said it is "the resolute stand of the DPRK to decisively foil all hostile acts and threats of aggression" through use of "Korean-style" nuclear deterrence.