Photo: The Canadian Press

South Korean President Moon Jae-in.

U.S. and South Korean troops kicked off their annual drills Monday that come after tensions rose over North Korea's two intercontinental ballistic missile tests last month.

The Ulchi Freedom Guardian drills are largely computer-simulated war games held every summer and have drawn furious responses from North Korea, which views them an invasion rehearsal.

Pyongyang's state media on Sunday called this year's drills a "reckless" move that could trigger the "uncontrollable phase of a nuclear war."

Despite the threat, U.S. and South Korean militaries launched this year's 11-day training as scheduled. The exercise involves 17,500 American troops and 50,000 South Korean soldiers, according to the U.S. military command in South Korea and Seoul's Defence Ministry.

No field training like live-fire exercise or tank manoeuvring is involved in the Ulchi drills, in which alliance soldiers, mostly senior officers, sit at computers to practice how they engage in battles and hone their decision-making capabilities.

The allies have said the drills are defensive in nature.

South Korea's President Moon Jae-in said Monday that North Korea must not use the drills as a chance to launch fresh provocation, saying the training is held regularly because of repeated provocations by North Korea.

North Korea test-launched two ICBMs at highly lofted angles last month, and outside experts say those missiles can reach some U.S. parts like Alaska, Los Angeles or Chicago if fired at normal, flattened trajectories.

Analysts say it would be only a matter of time for the North to achieve its long-stated goal of acquiring a nuclear missile that can strike anywhere in the United States.

Earlier this month, President Donald Trump pledged to answer North Korean aggression with "fire and fury." North Korea, for its part, threatened to launch missiles toward the American territory of Guam before its leader backed off saying he would first watch how Washington acts before going ahead with the missile launch plans.