North Korea fired a short-range ballistic missile into the sea off its east coast on October 14, South Korea's military said, the latest in a series of launches by the nuclear-armed country amid heightened tensions.
South Korea also scrambled fighter jets when a group of about 10 North Korean military aircraft flew close to the border dividing the two countries, and North Korea fired some 170 artillery shots off its east and west coasts, the South's Joint Chiefs of Staff (JCS) said.
South Korea's National Security Council condemned the North for escalating tension, calling its moves a violation of a 2018 bilateral military pact that bans "hostile acts" in the border area.
With the addition of 16 institutions and 15 North Koreans on a blacklist, Seoul imposed the first unilateral sanctions against Pyongyang in nearly five years.
As per North Korea's official KCNA news agency, the country's military said it took "strong military countermeasures" after South Korean artillery-fire drills on October 13.
The incidents happened in response to a KCNA report from October 13 that claimed that leader Kim Jong Un had overseen the launch of two long-range strategic cruise missiles on October 12 in order to verify the reliability of nuclear-capable weaponry deployed to military units.
North Korea's unusually frequent missile launches have sparked worries that it may be preparing to resume nuclear bomb testing for the first time since 2017. Some observers anticipate no tests before the Communist Party session in neighbouring China, which starts on October 16, comes to a conclusion.
South Korea's Joint Chiefs of Staff said the missile was launched at about 01:49 a.m. on October 14 (1449 GMT) from the Sunan area near North Korea's capital Pyongyang. It was at least the 41st ballistic missile launch by North Korea this year.
The South Korean JCS statement said the aircraft incident happened late on October 13 and early on October 14, Korean time.
The JCS said the aircraft were also seen near the eastern part of the inter-Korean border.
South Korea's presidential office said the artillery fire was a "regular, legitimate" military exercise.
North Korea has called its most recent series of missile tests, which included an intermediate-range ballistic missile that flew over Japan last week, a show of force against joint South Korean and US military drills.