PYONGYANG, Feb 18 (AFP) - North Korea fired at least one unspecified ballistic missile Saturday, South Korea's military said, Pyongyang's first test since the start of the year that comes days before Seoul and Washington are due to start joint tabletop exercises.

"North Korea fires an unidentified ballistic missile into (the) East Sea," South Korea's Joint Chiefs of Staff said, referring to the body of water also known as the Sea of Japan.

Tokyo also confirmed the launch, with the defence ministry saying that Pyongyang had launched a "possible ballistic missile," without giving further details.

Military tensions have risen on the Korean peninsula after a year in which North Korea declared itself an "irreversible" nuclear state, and carried out sanctions-busting weapons tests nearly every month.

In response, Seoul has ramped up joint military drills with key security ally Washington, in a bid to convince the increasingly nervous South Korean public of America's commitment to deter Pyongyang.

The Saturday launch -- Pyongyang's first since January 1 -- came days before Seoul and Washington are due to kick off a new tabletop exercise in Washington, in which the two allies will discuss how they would respond to the use of nuclear weapons by Pyongyang.

The exercise next week will focus on "joint planning, joint management and joint response with Washington's nuclear assets" in case of a nuclear attack by Pyongyang, a South Korean defence ministry official told AFP on Friday.

Pyongyang on Friday threatened an "unprecedentedly" strong response to upcoming US-South Korea drills, describing them as preparations for war.

If Washington and Seoul go ahead with the drills, "they will face unprecedentedly persistent and strong counteractions", a spokesperson for the North Korean foreign ministry said Friday.

South Korea's hawkish President Yoon Suk Yeol, who took office in May 2022, has vowed to get tough on the North, and had moved to quickly ramp up joint drills, which had been scaled back during the Covid pandemic.

They were also paused for a bout of ill-fated diplomacy with Pyongyang under his predecessor.