North Korea will surely "pay a price" for its escalating provocations, South Korea's top military officer said Friday, labeling a series of recent missile launches a "grave" threat to regional security as he held talks with the US air force commander.

Joint Chiefs of Staff (JCS) Chairman Gen. Kim Seung-kyum and US Pacific Air Forces Commander Gen. Kenneth Wilsbach held talks in Seoul earlier in the day to discuss the North's recent missile threat.

During the meeting, Kim said the allies' combined defense posture will "grow even stronger" and that the North will surely pay a price should the recalcitrant country continue its provocations, the JCS said in a statement.

The two also denounced the North's ballistic missiles launches this week as "grave provocative acts" that threaten the stability of the Korean Peninsula and the broader international society.

The two commanders also assessed the ongoing Vigilant Storm air drills as a "successful training event that verified the wartime combined operations execution posture" of the allies' air forces that "made the enemy shiver with fear," they added.

Pyongyang has recently escalated tensions on the peninsula with a barrage of missiles and artillery shells amid concerns it could conduct another nuclear test.

In Wednesday's provocation, the North fired more than 20 missiles, including one that landed south of the Northern Limit Line (NLL), the de facto inter-Korean maritime border, for the first time since the end of the 1950-53 Korean War.

On Thursday, it also test-fired an intercontinental ballistic missile (ICBM), marking its seventh such launch this year. The two allies decided to extend the Vigilant Storm practice, initially scheduled to end on Friday, in response to the North's ICBM launch. (Yonhap)