On Wednesday, US National Security Adviser Robert O'Brien said the speed of China's reaction to the emergence of the coronavirus had probably cost the world two months when it could have been preparing for the outbreak.
In a strongly worded tweet, written in English on his verified Twitter account, Chinese Foreign Ministry spokesman Zhao Lijian said it was the United States that lacked transparency.
"When did patient zero begin in US? How many people are infected? What are the names of the hospitals? It might be US army who brought the epidemic to Wuhan. Be transparent! Make public your data! US owe us an explanation!" Zhao wrote.
Zhao, an avid and often combative Twitter user, did not offer any evidence for his suggestion that the US military might be to blame for the outbreak in China.
Earlier on Thursday, Zhao's fellow Foreign Ministry spokesman Geng Shuang criticised US officials for "immoral and irresponsible" comments that blamed Beijing's response to the coronavirus for worsening the global impact of the pandemic.
Asked about O'Brien's comments, Geng told a daily news briefing in Beijing on that such remarks by US officials would not help US epidemic efforts.