North Korean leader Kim Jong Un inspects the defense detachment on Jangjae Islet in this undated picture released by the country's official news agency on May 5, 2017.

South Korea's Defense Ministry said the test-fired missiles were launched from North Korea's east coast near Wonsan city and traveled about 428 miles over the sea. Both projectiles reached an altitude of 30 miles and did not present a risk to the United States or South Korea.

The latest turn of events comes less than a week after North Korea test-fired two new short-range ballistic missiles , the first missile test since North Korean leader Kim Jong Un and President Donald Trump agreed to revive denuclearization talks last month.

The projectiles appeared to be a different type to previous launches, National Defense Minister Jeong Kyeong-doo said, according to South Korean news agency Yonhap.

The projectiles were launched from the Hodo Peninsula in South Hamgyong province on the country's east coast and flew about 250 km (155 miles), the South's Joint Chiefs of Staff said.

"We are aware of reports of a missile launch from North Korea and we will continue to monitor the situation," a senior Trump administration official told CNBC.

The Pentagon did not immediately respond to CNBC's request for comment.

In April, North Korea claimed to have "tested a powerful warhead" in the first public weapons test for the regime since Trump and Kim met for a historic summit in Singapore last year.

The two leaders held a second round of talks in Vietnam in February of this year, but negotiations collapsed after Trump reportedly handed Kim a note demanding he turn over the North's nuclear weapons and bomb fuel.

North Korea, the only nation to have tested nuclear weapons this century, spent most of Trump's first year in office perfecting its nuclear arsenal. The newest member of the world's exclusive nuclear weapons club has stopped testing of its nukes for now as the U.S. and international community offer the possibility of relief from crippling economic sanctions.

While North Korea has paused nuclear tests that prompted Trump's threat to bring "fire and fury" upon that country, it had already made significant progress before the historic dialogue with the U.S. started.

Under the third-generation North Korean leader, the reclusive state has conducted its most powerful nuclear test, launched its first-ever intercontinental ballistic missile and threatened to send missiles into the waters near the U.S. territory of Guam.

Since 2011, Kim has fired more than 90 missiles and had four nuclear weapons tests, which is more than what his father, Kim Jong Il, and grandfather, Kim Il Sung, launched over a period of 27 years.

—CNBC's Eamon Javers and Reuters contributed to this report.