In 15 other cities and towns, concentrations of particles in the air exceed what is considered to be a safe level, the statement said.

Those alerts have been issued in Debrecen, Dunaújvaros, Eger, Hernádszurdok, Miskolc, Pécs, Putnok, Sajószentpéter, Szeged, Szolnok, Szombathely, Tököl, Vác, Várpalota and Veszprém.

It added that in certain places the concentration of nitrogen dioxide in the air also exceeds what is considered to be a safe level.

The National Public Health Centre has asked residents of the cities in question to use public transport instead of their cars. It recommends that the most vulnerable groups should avoid outdoor physical activity and spend less time outdoors overall.