The United States on Friday sanctioned two Russian individuals and three entities over their support for North Korea's weapons program, the Treasury Department said.

The measures came a day after the Pentagon published an intelligence assessment that two recent North Korea missile launches were tests for a new intercontinental ballistic missile (ICBM) system.

The sanctions target "a network of Russia-based individuals and entities complicit in helping (North Korea) procure components for its unlawful ballistic missile systems," the Treasury under-secretary for terrorism and financial intelligence, Brian Nelson, said in a statement.

"Much of this activity also violates UN prohibitions with respect to the DPRK," the statement added, referring to North Korea's official name, the Democratic People's Republic of Korea.

North Korea has carried out numerous missile launches since the beginning of the year, claiming the two most recent tests were for satellite development.

A US official said the launches on February 26 and March 4 marked a "serious escalation." 

"The DPRK continues to launch ballistic missiles in blatant violation of international law, posing a grave threat to global security," Nelson said in the Treasury statement.

Washington and European allies on the United Nations Security Council failed Monday to convince China and Russia to back a text noting North Korea's "violations" of resolutions on missile technology.

Despite biting international sanctions over its nuclear weapons, Pyongyang has ignored US offers of talks since high-profile negotiations between leader Kim Jong Un and then-US president Donald Trump collapsed in 2019.

Instead of diplomacy, Pyongyang has doubled down on Kim's drive to modernize its military, warning in January that it could abandon a self-imposed moratorium on testing long-range missiles and nuclear weapons.