BEIJING -- Low visibility caused by fog and smog in large parts of China is disrupting traffic after the New Year holiday.

Dense fog temporarily closed several sections of six expressways in Beijing Tuesday morning, the first working day after the New Year holiday, according to Beijing Traffic Management Bureau.

In East China's Shandong province, 80 flights have been canceled or delayed at the airport in the capital Jinan City as of 11 a.m..

About 180 flights were canceled over the past two days in neighboring Henan Province, with visibility falling to just 10 meters Tuesday morning. The airport resumed operations in the afternoon, but the traffic may again be affected as more fog is expected Wednesday, according to the airport.

Many regions in China have been under heavy smog since Friday, disrupting traffic. Beijing on Sunday extended its orange alert for heavy air pollution until Wednesday midnight.

China's national observatory on Tuesday issued a red alert for fog and renewed an orange alert for smog in a number of northern, eastern and central regions.

China has a four-tier color-coded warning system for severe weather, with red being the most serious, followed by orange, yellow and blue.