Chinese state media outlets have urged investors not to panic after mainland markets plunged on Monday amid concerns over the spread of a new coronavirus.

Monday was the first trading day for mainland Chinese markets, after the government extended the Lunar New Year closure for financial markets in a bid to stem the spread of the virus. The Shanghai composite closed 7.72% lower, while the Shenzhen component and Shenzhen composite dropped 8.45% and 8.41%, respectively.

Government-backed Securities Times said in an op-ed on Tuesday that it's normal to see large fluctuations in markets following major events that occur suddenly, according to CNBC's translation of the Chinese-language text.

"Historically, there have been many events that caused panic such as the Sept. 11 terror attacks and SARS outbreak — but they eventually proved to be a one-time impact on markets," said the op-ed.

The new mysterious coronavirus has killed more than 420 people so far — majority of them in China. More than 20,000 cases in the country were confirmed by the end of Monday, according to China's National Health Commission.

Another state-affiliated media, China Securities Journal, said in an op-ed on Tuesday that the market decline is a "black swan" event that will not alter China's long-term fundamentals, according to CNBC's translation of the Chinese-language text.

The paper added that most of the negative economic impact from the virus outbreak will be felt in the first quarter. But the Chinese economy could stabilize after that with support from government, it said in the op-ed.

"Looking at the longer term ... there's no need to overestimate the impact of black swan events — such as a sudden public health threat — on the financial markets," it said.