The warning came amid a spate of missile tests by North Korea in recent weeks, including four ballistic missiles fired on Saturday, days after the United States and South Korea concluded their biggest-ever air force drills.

A statement from the General Staff of the Korean People's Army said it "will continue to correspond with all the anti-DPRK war drills of the enemy with the sustained, resolute and overwhelming practical military measures," using an acronym for North Korea's official name, KCNA reported Monday morning.

The statement also said the North's recent ballistic missile tests were a "clear answer" to Washington and Seoul over their joint exercises last week, calling the tests "corresponding military operations".

"The more persistently the enemies' provocative military moves continue, the more thoroughly and mercilessly the KPA will counter them," the statement said.

Hundreds of US and South Korea warplanes -- including powerful B-1B heavy bombers -- participated in the Vigilant Storm exercises last week, in the first time B-1Bs have flown to the Korean peninsula since December 2017.

The South Korean Joint Chiefs of Staff had said the move demonstrated the "capability and readiness to firmly respond to any provocations from North Korea".

Such exercises have long provoked strong reactions from North Korea, which sees them as rehearsals for an invasion.

The recent flurry of North Korean launches has included an intercontinental ballistic missile and one that landed near the South's territorial waters. South Korean President Yoon Suk-yeol has called the barrage "effectively a territorial invasion".