A no-fly zone declared by Russia over the Sea of Azov has come into effect.
Moscow issued the NOTAM (Notice to airmen) late on Sunday night barring commercial airliners from the area, which borders the crucial Ukrainian port of Mariupol, close to the line of contact between Ukrainian and pro-Russian separatist forces.
The move comes as a flotilla of Russian ships entered the sea on Sunday.
On Monday, authorities in Kyiv announced that 10 European airlines have suspended or cancelled flights to the country.
However, Infrastructure Minister Oleksander Kubrakov insisted that Ukrainian airspace remained safe and open.