The missiles, launched south of Musudan-ri, North Hamgyeong Province, were surface-to-surface KN-02 rockets with a range of up to 75 miles, an unidentified South Korean official told Yonhap news agency.
North Korea had declared waters off its east and west coasts off limits to boats from Oct. 10 to Oct. 20, Yonhap reported.
The missile launches, the first by North Korea since July, came days after North Korea said it was willing to jump start multiparty talks about its nuclear program with South Korea, China, Japan, the United States and Russia.
The United Nations passed tougher sanctions against North Korea after it conducted an underground atomic test in May.
Speaking from Northern Ireland, U.S. Secretary of State Hillary Clinton said the United States and its allies remain committed to a nuclear-free Korean peninsula. Monday's test-firing she said, would not affect that commitment.