International observers have determined that Soviet Grad rocket launchers had been used in the ongoing conflict in eastern Ukraine, according to a report released Monday.

According to the Organization for Security and Cooperation in Europe (OSCE), eight fresh craters related to shelling in the Krasnoarmeyskoye settlement reveal that Grad multiple launch rocket systems (MLRS, 122mm) were used from a westerly direction, hinting a probable Russian involvement.

Observations at the settlement of Telmanovo reach similar conclusions. “MLRS (122mm BM-21 Grad) fired from a west-south-westerly direction," Russia's Tass news agency quoted the OSCE report. "The SMM observed that some houses were heavily damaged and a transformer providing electricity to the village was destroyed."

During a declared ceasefire, nine people were killed Monday night as Russia-backed rebels and government troops got involved in an artillery exchange in eastern Ukraine, KOMO News reported. Even though the ceasefire was agreed upon in February, neither side has withdrawn heavy weapons from the region.

Leaders from France, Germany, Russia and Ukraine signed a peace agreement Feb. 12, with the ceasefire officially coming into effect at midnight Feb. 15.

According to an U.N. estimate, the conflict in eastern Ukraine killed 6,400 people since April 2014. The ceasefire was reportedly violated Monday after Ukraine and the pro-Russian separatists had failed to reach an agreement on withdrawing weapons.

Russian President Vladimir Putin did not make any comment about the recent shelling. However, he said that the present government in Ukraine was “not free” to make decisions as it was controlled by foreign powers. Putin said that the Ukraine was heavily influenced by Western countries including the United States.