North Korea launched two KN-01 short-range surface-to-ship missiles Thursday, Chosun Ilbo reported. JoongAng Ilbo said North Korea fired two similar missiles the previous day.
The New York Times said South Korean military officials would not comment on the reports although it is not uncommon for North Korea to test its short-range missiles.
The United States has demanded North Korea cancel next month's rocket launch, which would violate a U.N. Security Council resolution aimed at preventing North Korea from developing long-range missile technology.
North Korea has said it plans to launch a satellite between April 12 and 16 to celebrate the 100th birthday of the country's founder, Kim Il Sung.