Rebel forces shot down a military plane in Ukraine early Saturday morning, killing 49 servicemen that were onboard, Reuters reported.

The plane was carrying ammunition for government authorities and was about to land near the Russian border when pro-Russian separatists launched an anti-aircraft missile that struck and brought the aircraft down.

Wreckage from the plane could be seen scattered in a field where it crashed before daybreak near the eastern village of Novohannivka, Reuters reported. Nine crew members and 40 paratroopers were killed.

It is the highest amount of government forces killed in a single occurrence ever since conflict between separatists and government forces broke out in eastern Ukraine.

President Petro Poroshenko declared there would be an "adequate" response to the incident.

"All those involved in cynical acts of terrorism of this magnitude must be punished," the president said according to Reuters.

Several rebels raided the debris in search of the plane's ammunition. One rebel who identified himself as Pyotr said they will not stop attacking the government, which they often refer to as "fascists."

"This is how we work. The fascists can bring as many reinforcements as they want but we will do this every time. We will talk to them on our own terms," Pyotr said according to Reuters.

Russia has been accused of providing the separatists with weapons in an attempt to encourage the crisis in Ukraine, which used to be controlled by the former Soviet Union. On Friday, the U.S. State Department said Russia sent rocket launchers and other weapons to Ukraine.

"We assess that separatists in eastern Ukraine have acquired heavy weapons and military equipment from Russia, including Russian tanks and multiple rocket launchers," Marie Harf, a State Department spokeswoman, said in a statement obtained by Reuters.

Rebels claim they got the weapons from army stockpiles.

Russia has also denied any such influence in Ukraine.