Beijing has urged a scientific and professional explanation regarding the origin of the novel coronavirus after rising accusations that China was the source of the pneumonia-like disease.

High level U.S. officials including President Donald Trump have been calling it "China virus." National Security Adviser Robert O'Brien went even further, accusing the Chinese government of "covering up" the outbreak which as a result "cost the world community two months."

"We hope certain U.S. officials can focus on their domestic response and international cooperation instead of trying to shift the blame to China by denigrating the Chinese Government and people's efforts to fight the epidemic," said Chinese Foreign Ministry Spokesperson Geng Shuang on Friday.

The virus, first found in central China's Wuhan City last December, has been declared a "pandemic" by the World Health Organization recently. More than 4,750 people have died of the virus as of Friday with over 125,000 confirmed cases globally.

Late Thursday, another Chinese Foreign Ministry spokesperson Zhao Lijian suggested that U.S. is the one that lacks transparency in dealing with the outbreak.

The Beijing official cited Robert Redfield, director of the U.S. Centers for Disease Control and Prevention (CDC), addressing a U.S. Congressional committee on Thursday. Redfield confirmed that some coronavirus-related deaths have been found posthumously.

Zhao posted several tweets, demanding a further explanation from the U.S.

"CDC was caught on the spot. When did patient zero begin in U.S.? How many people are infected? What are the names of the hospitals?" he tweeted.

"It might be U.S. army who brought the epidemic to Wuhan," Zhao added, saying the U.S. should "be transparent" and "make public" all its data. 

The "US owe us an explanation," he wrote.