North Korea's military threatened Tuesday that it is ready to stage "ruthless" retaliation against South Korea and the United States over their ongoing joint military exercises.

North Korea's military stationed at the truce village of Panmunjom said that the US has ignored its warning to make the right choice, warranting Pyongyang's merciless punishment, according to the Korean Central News Agency.

The US will be wholly held accountable for the catastrophic consequences to be entailed by such reckless aggressive war maneuvers, as it chose a military confrontation (with North Korea)," its spokesman said in an English statement carried by the KCNA. 

It marked North Korea's first reaction to the 10-day joint military drills between South Korean and US troops which kicked off on Monday.

Pyongyang has denounced the drills as a rehearsal for invasion despite reassurances by Seoul and Washington that they are defensive in nature.

North Korea routinely issued warnings before and during the allies' drills, but this year it came amid heightened tensions between Washington and Pyongyang following exchanges of bellicose rhetoric.

US President Donald Trump warned of "fire and fury" if Pyongyang keeps endangering the US following Pyongyang's tests of intercontinental ballistic missiles in July.

In reaction, North Korea threatened to fire four ballistic missiles around the US territory of Guam, but its leader Kim Jong-un last week held off on the threats.

But he vowed to make an "important" decision if the US continues its "extremely dangerous reckless actions" on the Korean Peninsula, apparently referring to the military exercises.

The spokesman also took issue with visits to South Korea by three top US military commanders -- Pacific Command chief Adm. Harry Harris, Strategic Command head Gen. John Hyten and Missile Defense Agency Director Lt. Gen. Samuel Greaves.

They came here to observe the command-post exercises in person in what could be a move to show a strong alliance against North Korea's nuclear and missile threats. Gen. Joseph Dunford, the chairman of the US Joint Chiefs of Staff, also visited Seoul last week.

"Their visits are adding fuel to the gravity of the current situation," he said, adding that the US officers are in charge of preemptive strikes at North Korea.

Seoul's unification ministry declined to compare the level of North Korea's war rhetoric with last year's.

"South Korea is keeping close tabs on the North Korean military's activities," a ministry official said.

Foreign ministry spokesman Cho June-hyuck again stressed that the annual joint exercise is only for defensive purposes and is carried out legitimately.

"I cannot agree with the (North Korean) argument that the combined exercise would escalate tensions on the Korean Peninsula,"

he said. "The Ulchi Freedom Guardian exercise is a command post drill of a defensive nature that is conducted annually as part of the South Korea-US alliance. All aspects of it are conducted in a transparent manner."

The spokesman also said South Korea always stands prepared against the possibility of North Korea's strategic provocations, warning North Korea against pushing ahead with any provocations, including nuclear or long-range missile tests. (Yonhap)