North Korea launched six short-range missiles into the Sea of Japan immediately after Unite Nations Security Council imposed new sanctions on the country.
The missiles were fired from Wonsan at around 10am,South Korea's defence ministry spokesman Moon Sang-gyun said in a briefing, Yonhap news agency reported.
All missiles, with a target range of 100-150km, fell into the sea, the ministry said adding that the exact number of missiles is under examination.
United Nations Security Council unanimously adopted a resolution that vastly expands sanctions on North Korea after its nuclear and missile tests.
Under the tough new sanctions North Korean ships suspected of carrying illegal goods will be banned from ports across the world, while 16 new individuals and 12 organisations from North Korea have been blacklisted.
The sanctions are the strongest imposed by the Security Council in more than 20 years.
"Today, the international community, speaking with one voice, has sent Pyongyang a simple message: North Korea must abandon these dangerous programmes and choose a better path for its people," US President Barack Obama said in a statement.
The US was backed by China as it proposed to impose "tougher, more comprehensive" sanctions on Pyongyang after it carried out nuclear and missile tests.
"For the first time in history, all cargo going in and out of the DPRK (North Korea) would be subjected to mandatory inspection," US Ambassador to the UN Samantha Power had said.
Under the new sanctions, exports of coal, iron, gold, titanium and rare earth minerals from North Korea will be banned, and Pyongyang's supply of aviation fuel including rocket fuel will be blocked.
The new measures come after years of UN sanctions had done little to dissuade the North Korean regime from going ahead with its nuclear and ballistic missile programme.
Ten years after the country came under severe sanctions, Pyongyang said in early January it 'successfully' tested its first hydrogen bomb, exacerbating the security scenario in the region.
It was followed up with a rocket launch earlier this month, where Pyongyang claimed it placed an earth observation satellite into orbit. But that led to concerns that it was another milestone in Pyongyang's programme to build a long-range missile that can carry arsenal including nuclear weapons.