South Korea said a drone that crashed this week on one of its frontline border islands belongs to North Korea.
The small, unmanned aircraft was found on Baengnyeong island Tuesday, hours after the two sides exchanged artillery fire into the sea.
South Korean Unification Ministry spokesman Park Soo-jin said Wednesday an investigation has determined the plane is Pyongyang's.
"The relevant departments of the South Korean government have confirmed that North Korea is responsible for [the drone]," said Park.
Park would not comment on North Korea's purpose in operating the drone, though South Korean media reports have said it was conducting surveillance during the artillery exchange.
On Monday, North Korea fired 100 artillery rounds into the sea on the South Korean side of the maritime border, prompting Seoul to fire its own rounds back into northern waters. No one was injured in the exchange.
Tensions between the two Koreas have risen in recent weeks because of annual joint U.S.-South Korean military drills and a series of rocket and ballistic launches by Pyongyang.
In state media Wednesday, North Korean leader Kim Jong Un described the situation as "very grave." During a meeting with top military leaders, Kim blamed the U.S. "policy of hostility" for the increased tension.
Pyongyang threatened on Sunday to conduct what it called "a new form of nuclear test" after the U.N. Security Council condemned the North's recent ballistic missile launches.
The two Koreas remain in a technical state of war following their 1950s armed conflict, which ended in a truce and not a formal peace treaty.