Around 50 armed men, dressed in military uniforms without recognizable marks, arrived at the airport in three trucks, witnesses were quoted as saying.
These men, reportedly with "Russian Navy flags," surrounded the airport's domestic flights' terminal.
On Thursday, 100 gunmen wearing similar gear stormed the Crimean parliament and raised the Russian national flag on the top of the building.
Part of Russia's Black Sea Fleet is based in Sevastopol, Crimea. Moscow has raised security alert in borders with Ukraine by increasing fighter jet patrols in the area.