49 Ukrainian troops killed as transport plane downed in Lugansk (PHOTOS, VIDEO)

Forty-nine Ukrainian troops were killed when their military Il-76 transport jet was taken down by local militia forces just before it started its descent toward Lugansk Airport. Some military hardware and supplies were lost as well.

The death toll was confirmed by the Ukrainian General Prosecutor’s office on Saturday morning in a statement, which said nine crew members and 40 troops were killed.

Earlier the Defense Ministry said the troops were being transported to the Lugansk Airport for rotation along with military equipment and supplies.

Lugansk self-defense forces confirmed that they were behind the downing of the transport aircraft.

“It was hit with a rocket. We believe there were military troops on board,” a spokesman for the militia HQ told RIA Novosti.

The Il-76 is a heavy military transport aircraft that usually has a crew of seven and can transport up to 167 soldiers with weapons.

The downing of the plane overnight Friday was apparently the biggest single loss of Kiev loyalist forces, which has been waging a military crackdown on defiant eastern provinces for three months.

Ukrainian President Petro Poroshenko declared Sunday, June 15, a day of mourning for servicemen and border guards who died during the military operation. Poroshenko expressed condolences to the families of those who were killed on June 14 in the transport jet crash, saying that "Ukraine is mourning, but it will determinately continue its fight for peace."

"All those involved in the cynical act of terrorism of such scale will be definitely punished. Ukraine needs peace. But terrorists will get a proportionate response," said Poroshenko.

The president also ordered the meeting of the National security and defense council to be convened.

Meanwhile in Donetsk region, shooting resumed in Slavyansk and Kramatorsk late on Friday as the Ukrainian military continued its crackdown on self-defense forces in the country's east, a self-defense representative said.

Kiev’s military operation in eastern Ukraine has been intensifying. On Thursday, the Ukrainian military reportedly dropped phosphorous bombs on the town of Slavyansk.

Much of the village of Semyonovka, located in the Slavyansk suburbs, was set ablaze. Local residents told RT that the ground didn't stop burning for some time.

The use of incendiary bombs – designed to start fires using materials such as napalm, white phosphorus or other dangerous chemicals – is strictly prohibited by the UN.

Moscow demanded an immediate investigation into the reported use of incendiary bombs in Ukraine, Russian Foreign Minister Sergey Lavrov said on Thursday.