Ukraine has said it will ban Russian airlines from flying into the country as part of sanctions over Moscow's support for rebels in the east.
Kiev said the measures would take effect on 25 October and would include major Russian airlines Aeroflot and Transaero.
Russian transit flights will also be banned if the planes carry military personnel or dual-use goods.
Moscow described the move as "an act of madness", promising firm response.
In a separate development, Ukraine and Russia reached an agreement on supplies of natural gas to Kiev for the coming winter, ending month of tough negotiations.
The deal - brokered by the European Union - was initialled in Brussels. However, it requires "further procedures" before it can be signed.
Past gas disputes between Russia and Ukraine have led to interruptions in supply and caused major disruptions in shipments of Russian gas to EU countries.
Read more:
http://www.bbc.co.uk/news/world-europe-34365791
