The Ukrainian military accused separatists and Russian troops on Sunday of continuing to shoot at government forces despite a Sept. 5 ceasefire and said Kiev would not go ahead with setting up a proposed buffer zone until the truce violations stopped.
Ukraine's warring sides agreed on Friday to withdraw artillery and other heavy weapons to the outer limits of a 30 km (19 mile) buffer zone, building on the ceasefire in a conflict in eastern Ukraine that has killed more than 3,000 people.
Military spokesman Andriy Lysenko said the pro-Russian separatists and Russian troops were continuing to target the positions of government forces.
"In the last 24 hours we have lost two Ukrainian soldiers, eight have been wounded," he told reporters on Sunday.
Asked about the buffer zone, he said: "One of the main points of the agreement is the ceasefire, then other points follow.
"At the moment the first point has not been fulfilled 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," he said.
Lysenko said separatists had carried out a further attack on the government-held international airport of Donetsk, the east's main industrial hub. The rebels hold the city of Donetsk.
He said 40 separatist fighters had been killed in "defensive" fire by Ukrainian forces. There was no independent confirmation of this figure.
Ceasefire 'in name only'
Lysenko's comments echoed those of NATO's top military commander U.S. Air Force General Philip Breedlove, who said on Saturday that fighting was continuing in Ukraine and that the truce was a ceasefire "in name only".
"The situation in Ukraine is not good right now," U.S. Air Force General Philip Breedlove told reporters in the Lithuanian capital of Vilnius following a meeting of chiefs of defense of NATO countries. "Basically, we have a ceasefire 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 pre-ceasefire levels. The ceasefire is still there in name, but what is happening on the ground is quite a different story."
Donetsk was rocked by blasts on Saturday and a plant producing industrial explosives and military munitions appeared to have been hit.
The creation of a buffer zone was decided on Friday in a nine-point memorandum signed by the separatists and envoys from Moscow and Kiev.
The comments by Kiev and NATO underline the fragility of the ceasefire, which President Petro Poroshenko reluctantly called after Ukrainian forces suffered battlefield reverses which they ascribed to the direct intervention by Russian troops.
Moscow denies sending troops to Ukraine or arming the rebels, despite what Kiev and Western governments say is overwhelming evidence of direct Russian involvement.