Officials in Tehran have ordered schools, universities, government offices, and other institutions to close on January 5 because of high air pollution in the Iranian capital.
Only emergency and health services will report for work under the order from Morteza Tamadon, the Tehran governor.
The ISNA news agency said games in Tehran had also been called off to protect players' health.
Reports say the authorities are planning to impose restrictions on vehicle traffic to reduce pollution, while residents have been advised to avoid unnecessary travel.
It's the second time in a month that activities have been ordered halted in Tehran because of air pollution.
The Iranian capital is considered one of the dirtiest cities in the world, with many traffic jams involving aging, polluting cars.
Based on reporting by AFP and dpa