Eastern China smog

The smog seen in Istanbul for the last three days is due to intense air pollution, experts have stated, warning that citizens should not spend much time outside in the early hours of the day.

The fog that started to form in the early hours on the first days of the year in Istanbul increased with the sun rising.

Beijing is to raise the thresholds for issuing its highest air pollution warnings, the state news agency Xinhua reported on Feb. 22, two months after acrid smog triggered the city's first ever "red alerts." 

China warned residents across a large part of its north on Dec. 18 to prepare for a wave of choking smog arriving over the weekend, the worst of which is expected over Beijing, prompting the capital to issue its second ever "red alert."

Bulgaria's capital Sofia is covered by thick fog again on Tuesday morning, as the area is being hit by a cold spell over the past days.

Visibility is significantly reduced in neighborhoods and better in the central parts of the city.

On Monday, Sofia was among 9 regions where a Code Yellow alert was issued over dense fog.