Fighting continued this weekend around the pro-Russian separatist stronghold of Donetsk in eastern Ukraine despite a cease-fire agreement reached Sept. 5 and a related memorandum of understanding signed Friday. Gunfire was heard Sunday, the same day a planned buffer zone was supposed to become established, Agence France-Presse reported.

Agreement on the proposed buffer zone was reached Friday, Reuters reported. The Ukrainian government and the pro-Russian rebels committed themselves to moving heavy artillery out of an area about 18.6 miles wide as a way to support their recent cease-fire agreement. The Organization for Security and Cooperation in Europe would be in charge of monitoring the buffer zone. Despite this plan, Ukraine said the separatists have continued to fire at its troops and attacked the government-controlled Donetsk airport.

“At the moment, the first point has not been fulfilled [i.e., the cease-fire], so we are not talking about the other points. If there is to be a withdrawal of forces, then it should be synchronized together with the withdrawal of Russian forces,”  Andriy Lysenko, a Ukraine military representative, told reporters Sunday. Lysenko said two soldiers were killed, with another 8 wounded, during the clashes on Saturday.

U.S. Air Force Gen. Philip Breedlove, NATO’s top military commander, criticized the recent fighting in remarks made to reporters in Vilnius, Lithuania. He said there is a cease-fire “in name only. ... The number of events, and the number of rounds fired and the artillery used across the past few days, match some of the precease-fire levels. The cease-fire is still there in name, but what is happening on the ground is quite a different story.”

Ukraine and Western governments continue to assert Russia has provided weapons and troops to the separatists, a claim Moscow denies.