A US think tank says Russia may have provided technical support to North Korea for its development of intercontinental ballistic missiles.

The Center for Strategic and International Studies on Thursday released a report on its analysis of the Hwasong-18, a new type of ICBM launched by North Korea in July.

The report says the successful launch of the solid-fuel missile occurred only months after a horizontal engine test. It says the sudden appearance of these advanced capabilities is "difficult to explain without cooperation from the Russian government and its scientists."

The report says the physical dimensions and flight trajectory data of the Hwasong-18 are "nearly identical to that of the Russian Topol-M ICBM." It says the North Korean ICBM was likely developed with technical cooperation from Russia.

US National Security Advisor Jake Sullivan told reporters on Friday that the intelligence community is taking a hard look at the CSIS report.

He said Washington knows Russia has been seeking to obtain material for its war in Ukraine from North Korea. He added that as it has done with other countries, Russia will "usually also offer some types of security cooperation in return" and that the US is monitoring the situation closely reports NHK.