South Korea's Joint Chiefs of Staff said the missiles were fired at around 07:06 and 07:25 local time on Thursday from an area on the North's eastern coast.
The missiles flew 279 miles on an apogee of 37 miles before landing in the sea.
US Indo-Pacific Command spokesman, Captain Mike Kafka, said the US military was aware of the missiles and was monitoring the situation while closely consulting with allies.
"This activity highlights the threat that North Korea's illicit weapons programme poses to its neighbours and the international community," Capt Kafka said.
The launches came a day after US and South Korean officials said the North fired short-range weapons, presumed to be cruise missiles, into its western sea over the weekend.
North Korea has a history of testing new US administrations with missile launches and other provocations aimed at forcing the Americans back to the negotiating table.
Negotiations over the North's nuclear programme faltered after the collapse of Kim Jong Un's second summit with former US president Donald Trump in February 2019.
The North has so far ignored the Biden administration's efforts to engage, saying it will not take part in meaningful talks unless Washington abandons its "hostile" policies.
Mr Kim's sister recently berated the US over its latest round of combined military exercises with South Korea that ended earlier this month.
Just hours after Thursday's launches, South Korea Foreign Minister Chung Eui-Yong was to meet with visiting Russian Foreign Minister Sergey Lavrov in Seoul for discussions on North Korea and other regional issues.
South Korea's presidential office said it would hold an emergency National Security Council meeting to discuss the launches.
Since Mr Trump's first meeting with Mr Kim in Singapore in 2018, the North has not conducted nuclear or long-range missile tests, although analysts believe they have pressed ahead with their programmes on both.
The North has continued short and medium-range missile testing during its suspension of nuclear and long-range tests, expanding its ability to strike targets in South Korea and Japan, including US bases there.
Cover image: North Korean flag (Picture: imageBROKER/Alamy Stock Photo).