The training was part of a programme of "extended deterrence" against North Korea, it added.
The exercises came hours after a South Korean lawmaker claimed North Korean hackers had stolen a large cache of military documents from his country, "including a plan to assassinate North Korea's leader Kim Jong Un, and wartime contingency plans drawn up by the US and South Korea", reports the BBC.
Democratic Party representative Rhee Cheol-hee said in radio appearances on Wednesday that 235 gigabytes of military documents were taken from the Defense Integrated Data Center in September past year, citing information from unnamed South Korean defence officials.
The information, that included wartime contingency plans drawn up by the US and South Korea, was from the country's defence ministry, according to Rhee Cheol-hee, a South Korean lawmaker.
This year, North Korea tested an intercontinental ballistic missile that could potentially reach the USA mainland, and the US intelligence community assesses it has the technology to miniaturize a nuclear warhead atop it.
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In her statement, the Prime Minister suggested any Brexit agreement was a long time off and would come right down to the wire. The EU Parliament voted last week to block Brexit talks from moving onto discussions about Britain's future relationship .
About 235 gigabytes worth of military data was stolen by the hackers, Rhee said. "And I can tell you who is going to win".
In a pair of tweets sent Saturday afternoon, Trump said past agreements with North Korea have all been violated.
Hackers linked to North Korea reportedly targeted US electric power companies, according to a leading cybersecurity firm. In a speech at the United Nations in September, the US President accused the North Korean leader Kim of being "on a suicide mission" - while Kim responded by vowing to "tame the mentally deranged US dotard with fire".
Trump has engaged in an escalating war of words with North Korean strongman Kim Jong-Un, trading insults amid rising tensions between the two nuclear-armed rivals.
However, Trump said he still had confidence in the secretary of state. Rhee said 80 percent of the information hadn't been identified.
The U.S. has been pursuing a strategy of "maximum pressure" on North Korea, applying diplomatic and economic pressure multilaterally and unilaterally.