North Korea fired two cruise missiles from the west coast town of Onchon early this morning, a South Korean military source said.
The source added the South Korean and the United States military authorities are analysing details of the missiles' flight, including the range.
The launches come a day after Seoul and Washington kicked four days of preliminary joint drills in preparation for the long-suspended live field training Ulchi Freedom Shield, which takes place from 22 August to 1 September.
The two allies have scaled back combined military drills in recent years because of Covid-19 and to lower tensions with the North, which has accused the exercises of being a rehearsal for invasion.
Meanwhile, the Pentagon yesterday said the US, South Korea and Japan participated in a ballistic missile defence exercise off Hawaii's coast last week - the first such drills since 2017 as relations between Seoul and Tokyo hit their lowest in years.
While Pyongyang has not conducted a missile test for two months, it had battled against a Covid-19 outbreak for months before declaring victory over the virus last week. The North,however, has been observed preparing for a possible nuclear test, which would be its first since 2017.
In a separate news release made by the North on Thursday, the sister of its leader Kim Jong-un blamed propaganda leaflets from South Korea found near the border for causing the coronavirus outbreak and vowed a "deadly retaliation" against the South.
Despite such warnings, South Korean President Yoon Suk-yeol reiterated that he is willing to provide phased economic aid to North Korea if it ended nuclear weapons development and began denuclearisation, as he took questions during a news conference to mark his first 100 days in office.
