South Korea has confirmed that North Korea launched 2 missiles on Sunday.
South Korean military officials say the missiles were fired from a facility north of the city of Kaesong near the military demarcation line separating the 2 Koreas.
They say they were likely Scud missiles.
The officials say the first missile was launched at around 1:20 in the morning, and that the second launch took place about 10 minutes later.
They say the missiles travelled about 500 kilometers before falling into the Sea of Japan.
A US nuclear-powered aircraft carrier entered the South Korea port of Busan on Friday. The USS George Washington is to take part in a joint drill with Japan and South Korea.
Pyongyang is criticizing the port visit.
South Korean military officials say the North probably launched the missiles to protest the visit.
They also say the launches are aimed at showing the North's ability to carry out a surprise attack by firing missiles from a location close to the military demarcation line, which is unusual.
Jul. 13, 2014 - Updated 05:31 UTC