Travellers to northern and eastern China are set to face massive disruptions in air and road traffic as the country on Tuesday issued its first-ever red alert for severe fog.

The red alert -- the highest level in China's three-tier system of yellow, orange and red warnings for fog -- means visibility may fall below 50 metres within two hours. It is the first time the most severe warning for fog is being raised.

A large part of Beijing, Tianjin and Hebei would be shrouded in thick fog from Tuesday to Wednesday, the national observatory said. Other provinces including Henan, Shandong, Anhui and Jiangsu would also be affected.

Airports in those regions are bracing to suspend flights and highways might also be closed.

The observatory warned drivers in affected regions to slow down and airports, highways and ports to take necessary safety measures.

The red alert for fog is being issued as Beijing and other surrounding regions continue to reel from severe smog, with air quality index going off the charts in some areas on Sunday.

An orange alert for smog is still in effect in northern, eastern and central China. Hundreds of flights in those regions were suspended on Sunday.

Drone footage of cars queueing for kilometres to enter smog-stricken Beijing has sparked heated discussion online as residents brace themselves for more heavy air pollution in the coming days.

The gridlock occurred at a toll station near the capital on the Beijing-Hong Kong-Macau expressway at about 3pm on Monday as motorists waited to pay toll fees.

Internet users have poked fun at the traffic congestion.

One viewer commented: "Wow, so spectacular! It fully reveals the achievements of reforming and opening."

Another wrote: "Could I go there and sell beverages, boxed lunches and fruit?"

"I thought it was footage of a concert at first sight," another wrote.

Other social media users were glad they did not have to travel and could stay indoors.

"Why bother like this? I didn't drove my car during the three-day holiday - I was free of traffic jams and smog."

Others complained the smog. Wrote one: "It's so serious, but the government did not even apologise."

"The counter-urbanisation phenomenon could be accelerated because of the problems facing megacities including traffic jams and smog," one said.

Northern China is affected by heavy smog over the new year holiday, with many mainlanders complained of government inactions to tackle air pollution.

The Ministry of Environmental Protection said on Monday that it had punished over 500 enterprises and construction sites and 10,000 vehicles for breaching anti-smog measures. The ministry said 10 inspection teams found companies resuming production despite a government ban.