“The terrorists cynically and treacherously fired with a large-calibre machinegun hitting an Ilyushin-76 of the Ukrainian air force which was carrying troops on rotation and was about to land at Lugansk airport,” the ministry said in a statement.
The four-engine jet was also carrying “equipment”.
The ministry offered its condolences to the families of the “killed soldiers”, but did not give their numbers.
Lugansk, which is close to the Russian border, is the main city of one of two eastern regions hit by pro-Moscow separatist violence and which has declared its independence from Kiev.
An “anti-terrorist” clampdown by Ukrainian armed forces has left at least 270 people dead over the past two months.