The Biden administration on Wednesday imposed its first sanctions over North Korea's weapons programmes following a series of North Korean missile launches, including two since last week.

The sanctions targeted six North Koreans, one Russian and a Russian firm Washington said were responsible for procuring goods for the programmes from Russia and China, reports Reuters.

The US Treasury said the steps aimed both to prevent the advancement of North Korea's programmes and to impede its attempts to proliferate weapons technologies.

The United States also proposed that five of those individuals also be blacklisted by the United Nations Security Council, which would need consensus agreement by the body's 15-member North Korea sanctions committee.

The administration of US President Joe Biden has sought unsuccessfully to engage Pyongyang in dialogue to persuade it to give up its nuclear bombs and missiles since taking office in January last year.

US State Department spokesman Ned Price said the United States remained committed to pursuing diplomacy with North Korea.

"What we have seen in recent days ... only underscores our belief that if we are going to make progress, that we will need to engage in that dialogue," he told a regular news briefing.

The Treasury Department said the sanctions followed six North Korean ballistic missile launches since September, each of which violated UN Security Council resolutions.

Under Secretary of the Treasury for Terrorism and Financial Intelligence Brian Nelson said the moves targeted North Korea's "continued use of overseas representatives to illegally procure goods for weapons."

North Korea's latest launches were "further evidence that it continues to advance prohibited programs despite the international community's calls for diplomacy and denuclearisation," Nelson said in a statement.

It said the State Department had designated Russia-based North Korean Choe Myong Hyon, Russian national Roman Anatolyevich Alar and the Russian firm Parsek LLC for "activities or transactions that have materially contributed to the proliferation of weapons of mass destruction or their means of delivery."

It said Choe Myong Hyon, a Vladivostok-based representative of North Korea’s Second Academy of Natural Sciences (SANS), had worked to procure telecommunications-related equipment from Russia.

Four China-based North Korean representatives of SANS-subordinate organizations - Sim Kwang Sok, Kim Song Hun, Kang Chol Hak and Pyon Kwang Chol - and one other Russia-based North Korean, O Yong Ho, were also targeted.

Sim Kwang Sok, based in Dalian, had worked to procure steel alloys and Kim Song Hun, who was based in Shenyang, software and chemicals, Treasury said.

In a statement, US Secretary of State Anthony Blinken said that between at least 2016 and 2021, O Yong Ho had worked with Parsek LLC and Alar, the firm's director for development, to procure multiple goods with ballistic missile applications, including Kevlar thread, aramid fibre, aviation oil, ball bearings, and precision milling machines.

ROCKET FUEL MIXTURES

Blinken said Alar also provided O Yong Ho with instructions for creating solid rocket fuel mixtures.

"The procurement and supply relationship between O Yong Ho, Roman Anatolyevich Alar, and Parsek LLC is a key source of missile-applicable goods and technology for the DPRK’s missile program," his statement said.

It also said O Yong Ho had worked to procure items including aramid fibre, stainless steel tubes and ball bearings from "third countries" it did not name.

North Korea's UN mission, Russia and China's embassies in Washington and the Russian firm did not respond to requests for comment.

North Korean media said leader Kim Jong Un observed the test of a hypersonic missile on Tuesday, the second in less than a week after he vowed in a New Year speech to bolster the military with cutting-edge technology.

Tuesday's test came hours after the US mission to the United Nations, joined by Albania, France, Ireland, Japan and the United Kingdom, condemned last week's launch and called on UN states to fulfill sanctions obligations.

UN resolutions ban North Korean ballistic missile and nuclear tests and impose sanctions.

Anthony Ruggiero, a sanctions expert in the former Trump administration that failed to persuade Kim to roll back his nuclear programme despite unprecedented engagement, called the new sanctions "a good start."

However, he said the Biden administration had allowed a reversal of sanctions pressure and added: "Biden needs to continue the designations to increase the pressure on the Kim regime."

Price did not respond when asked why no Chinese individuals or entities were targeted, or specifically when asked if China and Russia were doing enough to enforce sanctions, but stressed the importance of all UN states doing so, while adding: "Obviously we've not seen all of that."

Wednesday's actions freeze any US-related assets of those targeted and prohibit all dealings with them.