North Korea fired at least one projectile towards its eastern sea on Thursday,South Korea’s military said.
Seoul’s Joint Chiefs of Staff did not immediately confirm whether the weapon was a rocket, artillery or a ballistic missile, or how far it flew.
“We are maintaining readiness and monitoring in case of additional launches,” it said in a statement.
The North’s latest launch follows statements of displeasure over the slow pace of nuclear negotiations with the United States and demands the Trump administration ease sanctions on Pyongyang.
Earlier this month, North Korea test-fired an underwater-launched ballistic missile for the first time in three years.
The North then walked away from working-level nuclear talks with the US in Sweden, and has since repeatedly urged Washington to come forward with a new offer by the end of the year.
Pyongyang is under multiple sets of international sanctions over its banned nuclear weapon and ballistic missile programmes, which it says it needs to defend against a possible US invasion.
News of the launches came after South Korea said earlier Thursday that North Korean leader Kim Jong Un sent a message of condolence to South Korean President Moon Jae-in over his mother’s recent death.
The two leaders met three times last year and struck a set of deals aimed at easing animosity and boosting exchanges. But in recent months, North Korea has drastically reduced its engagement and diplomatic activities with South Korea, after Seoul failed to resume lucrative joint economic projects held back by US-led UN sanctions.
Last week, Kim ordered the destruction of South Korean-built facilities at a long-shuttered joint tourist project at a North Korean mountain. South Korea later proposed talks but North Korea has insisted they exchange documents to work out details of Kim’s order.