North Korea launched a ballistic missile off its east coast on Monday, South Korea's military said, a day after the North vowed "offensive and overwhelming" responses to protest a new U.S. military drill with South Korea and Japan.

The Joint Chiefs of Staff said the launch was made on Monday morning, but gave no further details, including how far the weapon traveled.

The launch came two days after South Korea, the U.S. and Japan ended their new multidomain trilateral drills. The "Freedom Edge" drill drew a U.S. aircraft carrier and destroyers, fighter jets and helicopters from the three countries, and the three countries practiced missile defense, anti-submarine and maritime interdiction drills.

On Sunday, North Korea's Foreign Ministry issued a lengthy statement strongly denouncing the U.S., South Korea and Japan over their three-way drill. It called the drill an Asian version of NATO that openly destroys the security environment on the Korean Peninsula and contained a U.S. intention to exert pressure on Russia and lay siege to China.

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The North's Foreign Ministry said it will "firmly defend the sovereignty, security and interests of the state and peace in the region through offensive and overwhelming countermeasures."

Monday's launch was the North's first weapons firing in five days. Last Wednesday, North Korea launched what it called a multiwarhead missile in the first known launch of a developmental, advanced weapon meant to defeat U.S. and South Korean missile defenses. North Korea said the launch was successful, but South Korea dismissed the North’s claim as deception to cover up a failed launch.

In recent weeks, North Korea has floated numerous trash-carrying balloons toward South Korea in what it has described as a tit-for-tat response to South Korean activists sending political leaflets via their own balloons.

Meanwhile, North Korea opened a key ruling party meeting Friday to determine what it called "important, immediate issues" related to works to further enhance Korean-style socialism. On the meeting’s second-day session Saturday, leader Kim Jong-un spoke about "some deviations obstructing" the county’s efforts to improve its economic status and unspecified important tasks for resolving immediate policy issues, North Korea’s state media reported Sunday.