China has warned its nationals in Kazakhstan of an "unknown pneumonia" that has hit the central Asian country since mid-June. 

In a statement on Thursday, China's embassy in the Kazakh capital Nur-Sultan warned that the mortality rate of the disease was "much higher" than that of the novel coronavirus.

"Kazakhstani Health Department and other agencies are conducting comparative research and have not defined the nature of the pneumonia virus," it added.

Urging Chinese citizens to follow government guidelines, the statement said people should "minimize outings, and avoid crowded public places."

It noted that the rise in cases of the disease had been concentrated in the regions of Atyrau, Aktobe and Shymkent.

"So far, nearly 500 people have been infected and more than 30 people are critically ill," the statement said.

"In the first half of this year, pneumonia caused 1,772 deaths. In June alone, 628 people died, including Chinese citizens."

COVID-19 national mourning day

Meanwhile, Kazakhstan President Kassym-Jomart Tokayev has signed has signed a decree declaring the "day of nationwide mourning" in memory of COVID-19 victims on July 13.

"It is a common tragedy for all of us. That’s why I decided to declare July 13 the National Day of Mourning for people who died from pandemic. I am confident that all of us will honor the memory of those who died on that very day," news agency Kazinform cited Tokayev as saying on Wednesday in a televised speech.The Central Asian country has reported 53,021 cases of the coronavirus. 35,137 patients have recovered, while 264 people have died due to the virus.