Steph Solis and John Bacon

USA TODAY

North Korea fired five short-range ballistic missiles into waters off the country's east coast Monday in an apparent rebuke of joint military exercises underway between the United States and South Korea.

The missiles were launched from a site near the northeastern city of Hamhung and flew about 125 miles before landing in waters off North Korea’s east coast, South Korea’s Joint Chiefs of Staff said.

"We are aware that (North Korea) launched five short-range ballistic missiles today," said Cmdr. Bill Urban, a Pentagon spokesman. He called the launches a "clear violation of multiple U.N. Security Council resolutions."

Hours after the missiles were launched, South Korea and the United States began talks in Seoul on implementing new United Nations sanctions imposed on the North over its nuclear test in January and long-range rocket launch last month. Pyongyang has repeatedly issued nuclear strike threats against both Seoul and Washington.

Ambassador Sung Kim, U.S. special representative for North Korea policy, said the two nations are "fully committed to implementing the (U.N.) resolution with vigor and energy," South Korea's Yonhap News Agency reported. "Both countries are also reaching out to others in the region and beyond to ensure everyone is implementing this important resolution fully."

North Korea fires ballistic missile into sea

On Friday, North Korea fired a medium-range missile into the Sea of Japan, the first time the country fired a medium-range missile since early 2014. The country has fired several short-range missiles off its east coast since the U.N. imposed broad sanctions in response to its nuclear and missile tests.

More than 15,000 U.S. personnel and an estimated 300,000 South Korean forces are participating in the "Key Resolve" computer-simulated command-post exercise and the "Foal Eagle" field training exercise, a markedly larger force than in recent years.

Alison Evans, senior analyst at IHS Country Risk in London, said the annual U.S.-South Korea military exercises that began two weeks ago routinely increase risks of a clash with North Korea. Evans said the larger scale of this year's exercises have aggravated that risk.

Evans also said North Korea's deteriorating relations with China adds to the instability.

"If relations with China do not improve, increasing economic hardship in North Korea may well make more provocative action a logical option for the leadership," Evans said.

After Friday's launch, State Department spokesman John Kirby called on North Korea to "refrain from actions that further raise tensions in the region and focus instead on taking concrete steps toward fulfilling its international commitments and obligations," according to a statement.

Kirby said the U.S. is closely monitoring the situation on the Korean Peninsula.

Obama imposes more North Korea sanctions