North Korea fired three ballistic missiles into its eastern sea, after a week of verbal warnings over the South's decision to deploy an advanced US missile defence system, Seoul said.
The short-range missiles were launched from inland and flew about 310 to 375 miles before crashing into the sea.
They displayed a sufficient range to target the southern part of South Korea, where Seoul and Washington have decided to station the Terminal High-Altitude Area Defence, or THAAD, system, Seoul's Joint Chiefs of Staff said.
The Pentagon said US Strategic Command systems tracked "what we assess were three North Korean missile launches".
It said two were presumed to be Scud tactical ballistic missiles "followed by the presumed launch of a No Dong intermediate range ballistic missile".
It said the missile launches did not pose a threat to North America.
North Korea routinely test fires short-range missiles and artillery systems but it tends to do more launches in times of tension with the outside world.
It launched what was presumed to be a ballistic missile from a submarine on July 10, according to US and South Korean officials, a day after US and South Korean military officially announced they would deploy the THAAD system in South Korea.
South Korea's defence ministry announced last week that the south-eastern rural town of Seongju had been picked as the site for the THAAD deployment.
Seoul and Washington had been discussing deploying the THAAD system since North Korea conducted a fourth nuclear test and a long-range rocket launch earlier this year.
The North said last Monday that it will take "physical counter-action" as soon as the THAAD location was announced and has issued further warnings through its state media after Seongju was confirmed as the site.