North Korea has fired two short-range missiles into the sea, South Korea's Joint Chiefs of Staff (JCS) said.
They were launched over the sea early on Thursday, from Wonsan on North Korea's east coast.
A JCS official said at least one of the missiles travelled about 690km (428 miles) and appeared to be a new design.
It marks the first time North Korea has fired any missiles since leader Kim Jong-un's impromptu meeting with Donald Trump late last month.
It also comes after anger from the North over planned military exercises between South Korea and the US, an annual event. The North warned they could affect the resumption of denuclearisation talks.
The first missile was launched at about 05:34 Thursday local time (20:34 GMT Wednesday) and the second at 05:57, said the JCS.
Initial reports said both missiles travelled about 430km, reaching an altitude of 50km, before falling into the Sea of Japan, also known as the East Sea.
But after analysis from US and South Korean intelligence officials, the JCS said at least one was likely to have been a "new type of missile".
Japan's defence minister said the launches did not reach Japanese waters and had no immediate impact on its national security.
It is not clear if North Korean leader Kim Jong-un oversaw Thursday's launch.
South Korea's defence ministry has urged Pyongyang to stop acts that it said were unhelpful for easing tension, reported Reuters.
'North Korea is clearly upset'
After an invitation on Twitter in June, US President Donald Trump and his counterpart Mr Kim had an impromptu meeting at the demilitarised zone that divides the two Koreas, where they agreed to restart denuclearisation talks.
Following that US Secretary of State Mike Pompeo said working-level talks would likely start in July, but there have been no further public meetings between US and North Korean officials.
But North Korea has condemned the planned US-South Korea military drills next month, calling it a "violation of the spirit" of the joint statement signed by Mr Trump and Mr Kim at their first face-to-face talks in Singapore last year.
Though the US and South Korea have refused to cancel the military exercises, they have been scaled back significantly.
"North Korea is clearly upset that the US and South Korea are conducting joint military exercises," Harry Kazianis of Washington's Center for the National Interest told news agency Reuters.
Last year, Mr Kim said North Korea would stop nuclear testing and would no longer launch intercontinental ballistic missiles.
Nuclear activity appears to be continuing, however, and satellite images of North Korea's main nuclear site last month showed movement, suggesting the country could be reprocessing radioactive material into bomb fuel.
Pyongyang also continues to demonstrate its abilities to develop new weapons despite strict economic sanctions. Earlier this week Mr Kim inspected a new type of submarine, state media reported, which could be developed to carry ballistic missiles, according to some analysts.
Pyongyang also conducted a similar short-range missile launch in May, its first such test since its intercontinental ballistic missile launch in 2017.
Mr Trump had responded then by saying he believed Mr Kim would not do anything that could jeopardise his country's path towards better relations.
He had tweeted that Mr Kim "knows that I am with him and does not want to break his promise to me".