Ukraine has banned all Russian planes from using its airspace and exports of Russian gas to Ukraine have been halted by state-controlled giant Gazprom.
The decision was announced by Ukrainian Prime Minister Arseniy Yatsenyuk at a televised government meeting.
Gazprom said it had halted gas deliveries to Ukraine because it had used up all the gas it had paid for.
But Ukraine said it had stopped buying from Gazprom because it could get cheaper gas from Europe.
The airspace ban applies to military planes as well as civil airliners.