The test of a new high-thrust rocket engine was hailed as a "great leap forward" by North Korea, state media reported Sunday.
The news agency added that Kim Jong Un studied the engine's technical specifications ahead of the test and then guided the test.
Chinese President Xi Jinping and US Secretary of State Rex Tillerson pledged in talks yesterday that the two powers would work to strengthen a relationship that has been unsettled by disputes over North Korea and trade. It was developed without "dependence on the technology of other countries", KCNA said.
Malaysian police have previously identified eight North Koreans wanted for questioning in connection with the killing of Kim Jong Nam, some of them hiding in the North Korean embassy.
"There is nothing about this rocket engine itself that makes me more terrified, but taken as a whole, it's pretty clear that they are trying to give us proof of their growing missile program", Hanham said.
U.S. president Donald Trump's new right hand man Rex Tillerson met with his Chinese counterpart on Saturday.
In his New Year address, Kim Jong-un said his country's ICBM development program was "at its final phase", raising the prospect of the North's firing an ICBM missile this year. "Although I can't reveal who they are, we believe there is an "important person" among them", he told state media.
En route to Beijing, Tillerson visited United States allies Japan and South Korea where he declared Washington would drop the "failed" approach of patient diplomacy with Pyongyang, warning that American military action against the North was "on the table".
North Korea has been referring to the deceased as Kim Chol, the name that appeared in the victim's passport, and has rejected the police findings that VX was used to kill him. "China has done little to help!"
On his visit to Seoul Friday, Tillerson proclaimed that the existing policy of strategic patience from the previous Obama administration had "ended", in a strong indication of the Trump administration's readiness for a bolder stance against the Pyongyang regime.
Kim has said he's close to developing an intercontinental ballistic missile capable of reaching North America.