The novel coronavirus is from nature, and accusations from the United States that a Chinese lab was the source of the pandemic are unprofessional, a top Russian virologist said.

Alexander Semyonov, head of the Yekaterinburg branch of the State Research Center of the Virology and Biotechnology Vector Institute, said these claims are groundless and added it was "pure fantasy" to think that a coronavirus could be created using artificial methods.

"The virus came from nature, and, so far, I have not found any reasons to change my opinion. The accusation about a man-made coronavirus is unreasonable, unprofessional and stupid," Semyonov said.

Semyonov was one of the members of the China-WHO joint expert team that visited China in February last year to research the origins of the novel coronavirus.

He slammed the hyping up of the "lab leak" theory in the US as an attempt to falsely blame China.

"It is a pity that the research of such an epidemic has involved many political factors."

"Amid the current China-US relationship, blaming China would benefit the US," he said.

Semyonov said that the previous US administration had a hostile attitude toward China, "and it seems that the Biden administration is not so different from its predecessor on the origin of COVID-19".

Semyonov's conclusions were shared by Chinese Ambassador to Russia Zhang Hanhui, who urged the US to cooperate with the international community on tracing the origins of the virus, instead of politicizing the issue.

"If the US indeed aspires to truth and transparency, it must agree to an international investigation on the coronavirus and identify the source of the epidemic in the US and the reasons for its incompetent response," Zhang said at a news conference in Moscow on July 21.

He said Washington displayed an unscientific approach to researching the origins of the virus.

"This is a job for scientists", not the CIA, to determine the origins of the coronavirus, he said.

China has always upheld the principles of openness, transparency and cooperation on the investigation of the origins of COVID-19, but some US politicians only sought to politicize scientific matters, Zhang said.