South Korea and a US strike force led by the nuclear-powered aircraft carrier USS Nimitz kicked off Monday a joint naval drill slammed by North Korea as a "wanton" provocation and rehearsal for war.
The two-day exercise began with the departure of the 97,000-tonne Nimitz, one of the world's largest warships, from the southern South Korean port of Busan where it had been docked over the weekend, the US navy said in a statement.
"The operations include integrated flight operations, air defense events, surface warfare training events, precision ship maneuvers, and liaison officer exchanges," it said.
A number of other naval ships including guided-missile cruisers and a guided-missile destroyer will also take part in the drill designed to "reinforce regional security and stability", it added.
The exercise comes as the Korean peninsula is only just emerging from a period of highly elevated military tensions triggered by North Korea's nuclear test in February.
Angered by UN sanctions imposed after the test and by a series of large South Korean-US military drills, Pyongyang spent much of March and April issuing dire warnings including threats of nuclear strikes against Seoul and Washington.
The North called the latest exercise with the Nimitz "a grave military provocation" that would trigger a fresh cycle of escalating tensions.
"This is a wanton threat against us... that will push the peninsula to the brink of nuclear war," Rodong Sinmun, the official newspaper of the North's ruling party, said in an editorial on Monday.
"How could we ever ignore the arrival of such dangerous forces to the South?" it said.
"The warmongers... should never forget that our forces stand fully ready to attack at once in line with operational plans approved by our top command," the newspaper added.
North Korean troops near the disputed Yellow Sea border have been ordered to strike back if "even a single shell drops" in their territorial waters, the North's army command said in a recent statement.
Any subsequent counterstrike would trigger an escalated military reaction that would see South Korea's border islands engulfed in a "sea of flames", it said.
The tense sea border off the west coast saw deadly naval clashes in 1999, 2002 and 2009. The North shelled one of the islands, Yeonpyeong, in November 2010, killing four South Koreans and sparking brief fears of a full-scale conflict.