North Korea's military fired a missile Wednesday that crossed the disputed maritime border with South Korea for the first time since the countries' division in 1948, officials in Seoul said.

The big picture: Seoul responded by firing three missiles following the launch of Pyongyang's short-range ballistic missile, which landed some 37 miles from the South Korean city of Sokcho and caused air-raid sirens to sound on Ulleungdo island, per the BBC.

By the numbers: The missile was one of three launched from the North Korean coastal area of Wonsan into the sea, according to South Korea's Joint Chiefs of Staff.

For the record: Pyongyang's missile landed outside of South Korean waters and south of the Northern Limit Line Northern Limit Line — the de facto sea boundary drawn by the UN at the end of the 1950-53 Korean War.

What they're saying: South Korean President Yoon Suk-yeol said Pyongyang's actions were an "effective act of territorial encroachment," Reuters reports.

Editor's note: This is a breaking news story. Please check back for updates.