Japan's public broadcaster and other media, citing Japanese and U.S. sources, reported that the missiles were surface-to-ship. Japanese Defense and Foreign Ministry officials said they could not immediately confirm the reports.
"At the moment, we have not confirmed the report and there is no announcement," Foreign Ministry spokesman Noriyuki Shikata said.
Public broadcaster NHK said the short-range missiles were fired on the east and west coast of the Korean Peninsula earlier Friday. Officials are currently investigating further details, including the number of missiles fired. NHK said the missiles were shorter-range, and were not North Korea's existing Rodong or Taepodong I ballistic missiles.
Japan's NTV network reported that the missiles were surface-to-ship.
It was not immediately known where they landed.
The broadcaster suggested that the North's test was in response to South Korea's launch of its first destroyer equipped with high-tech Aegis radar technology on Friday.
Kyodo News agency said the missiles were launched from Hamgyong Namdo on the east coast of the Korean Peninsula and are considered modified silkworm or miniturized Scuds, with a range of about 100-200 kilometers (60-125 miles).
Mobile missile carriers, communication equipment and personnel had been seen in the area before the launch, but they left after the missiles were fired, Kyodo said.
South Korea's Joint Chiefs of Staff said it was checking the report. The Defense Ministry had no comment.
But Yonhap news agency reported, citing an unidentified military source, that the South had confirmed the launches and was trying to identify the types and the number of missiles fired.
Last month, North Korea displayed a newly developed ballistic missile capable of reaching the U.S. territory of Guam during a massive military parade.
The parade in Pyongyang featured three new models, including the medium-range missile that can travel 2,500-4,000 kilometers (1,500-2,500 miles), the South Korean newspaper Chosun Ilbo reported.
The report cited an unidentified South Korean government official familiar with an analysis of U.S. satellite images.
North Korea's missile development has been a constant concern to the region, along with its pursuit of nuclear weapons.
The hard-line regime test-fired a series of missiles in July last year, including its latest long-range model, known abroad as the Taepodong-2, which experts believe could reach parts of the United States.
The North rattled the world again in October by conducting its first-ever test of a nuclear device. However, experts believe it does not have a bomb design advanced enough to be placed on a missile.