- Communications then dried up, despite a third encounter in the Demilitarized Zone that divides the Korean peninsula.
SEOUL: North Korea fired a projectile into the sea early Thursday, the South's military said, in what could be its first ballistic missile test during the administration of Joe Biden.
Seoul's joint chiefs of staff said in a statement that the "unidentified projectile" was launched into the Sea of Japan, known as the East Sea in Korea.
No further details of the device type, or how many were fired in total, were immediately available.
The nuclear-armed North is banned from developing ballistic missiles under UN Security Council resolutions.
But it has made rapid progress in its capabilities under leader Kim Jong Un, testing missiles capable of reaching the entire continental United States as tensions mounted in 2017.
It has a long history of using weapons tests as a provocation, in a carefully calibrated process to forward its objectives.
Thursday's launch comes after Pyongyang fired two short-range, non-ballistic missiles in a westerly direction towards China at the weekend.
That followed joint exercises by the US and South Korean militaries and a visit to the region by US Secretary of State Antony Blinken and Defence Secretary Lloyd Austin to discuss alliance and security issues.
During their trip to Seoul and Tokyo, Blinken repeatedly stressed the importance of denuclearising Pyongyang.
That prompted North Korean first vice foreign minister Choe Son Hui to accuse the US of a "lunatic theory of 'threat from North Korea' and groundless rhetoric about 'complete denuclearisation'."
Pyongyang had been biding its time since the new administration took office, not even officially acknowledging its existence until last week.
Washington is reviewing its approach to the North after a tumultuous relationship between president Donald Trump and leader Kim, which went from trading insults and threats of war to a diplomatic bromance and several meetings, but made no substantive progress towards denuclearisation.
Trump held two headline-grabbing summits with Kim, in Singapore and Vietnam, and the United States pulled back on some joint training activities with South Korea's military while North Korea froze intercontinental ballistic missile tests.
But their February 2019 meeting in Hanoi broke up over sanctions relief and what the North would be willing to give up in return.
Communications then dried up, despite a third encounter in the Demilitarized Zone that divides the Korean peninsula.
The two-month-old Biden administration hopes to restart negotiations on the North's nuclear arsenal but officials say there has been no response to their initial outreach.
US officials are now finalising a strategy to restart talks that the White House will discuss with Japanese and South Korean security officials next week, an administration official said.