A Ukrainian military helicopter exploded at the Kramatorsk airbase in eastern Ukraine after it was hit by a sniper, according to Kiev officials.
"An army Mi-8 helicopter has exploded at the Kramatorsk aerodrome," the defence ministry in Kiev said.
Ukrainska Pravda website reported that two explosions were heard at the military base.
Dmitry Tymchuck, head of the centre for military and political research, said the helicopter was hit just before take-off. The pilot managed to jump out of the craft unharmed and there were no reports of injuries.
Anti-terrorism chief Vasily Krutov in Kiev said the helicopter was hit by a single shot.
An airport worker added that an AN-2 plane had also been destroyed and one person wounded, although there was no official confirmation of that.
Pro-Russian militants claimed responsibility for the attack, according to Russia-state run news agency RIA Novosti.
Rebels had attempted to seize the airfield but were rebutted by Ukrainian forces.
Ukraine's interim prime minister Arseniy Yatsenuk accused the Kremlin of aiming to occupy Ukraine and push Europe into war.
Ukrainian troops were carrying out a "second stage" of the military operation in eastern Ukraine aimed at crushing pro-Russian "terrorists", according to Sergey Pashinsky, the interim head of the presidential administration appointed by Ukraine's Verkhovna Rada (parliament).