North Korea test fired two medium-range ballistic missiles on Friday, just days after leader Kim Jong-Un promised a series of nuclear warhead tests and missile launches amid surging military tensions.

North Korea test fired two medium-range ballistic missiles on Friday, just days after leader Kim Jong-Un promised a series of nuclear warhead tests and missile launches amid surging military tensions.

Friction on the divided Korean peninsula has deepened since the North carried out its fourth nuclear test on January 6, followed a month later by a long-range rocket launch that was widely seen as a disguised ballistic missile test.

U.S. defense officials said they had tracked two launches -- both believed to be medium-range Rodong missiles fired from road-mobile launch vehicles.

The Rodong is a scaled-up Scud variant with a maximum range of around 1,300 kilometers (800 miles).

South Korean military officials said the first missile was launched from Sukchon in the country's southwest at 5:55 am (2055 GMT Thursday) and flew 800 kilometers before splashing down in the East Sea (Sea of Japan).

The second, fired about 20 minutes later, disappeared off radar early into its flight.

They came a day after U.S. President Barack Obama signed an order implementing tough sanctions adopted earlier this month against North Korea by the U.N. Security Council, as well as fresh unilateral U.S. measures.