Two Ukrainian military jets were shot down in the east of the country July 23, less then a week after the downing of a Malaysian passenger plane.
Ukraine's military spokesman Oleksiy Dmytrashkivsky said the fate of the pilots is unknown.
The separatists had claimed earlier that they shot down one Su-25 jet near Snizhne. They said a second Su-25 was hit and damaged but flew away.
Malaysian Airlines Boeing-777 flying from Amsterdam to Kuala Lumpur was shot down July 17 on the territory of Ukraine, near the border with Russia. All the 298 people on the board died.