Schools and universities have been shut in parts of Iran including the capital, Tehran, due to high levels of pollution, state media report.
The decision to shut schools and universities in the capital on November 30 was announced late on November 29 by Deputy Governor Mohammad Taghizadeh, after a meeting of an emergency committee for air pollution.
"Due to increased air pollution, kindergartens, preschools and schools, universities, and higher-education institutes of Tehran Province will be closed," Taghizadeh was quoted by official government news agency IRNA as saying.
Schools in the capital will also be closed on December 1, Taghizadeh said later.
"Having examined the index of pollutants in Tehran...it was decided for all schools to be closed tomorrow in Tehran Province, except for the counties of Firuzkuh, Damavand, and Pardis," he was quoted as saying.
The young and elderly and people with respiratory illnesses were warned to stay indoors and all sports activities were suspended on November 30.
Tehran has suffered from dangerous levels of pollution and smog since mid-November.
Schools were also closed in the northern province of Alborz and in the central province of Isfahan, IRNA reported, citing officials.
Other areas where schools were shut included the northeastern city of Mashhad, the northwestern city of Orumiyeh, and Qom, south of Tehran.