Some 17,600 servicemen, who had participated in military drills ion the border with Ukraine, would be pulled back.
“There is no contradiction between a strong NATO and building constructive relations with Russia,” said Stoltenberg.
It was the largest single number of Ukrainian soldiers killed since a fragile ceasefire came into force on Sept. 5.
Kiev and pro-Russian rebels are supposed to pull back their forces and weaponry to create a 30-kilometre wide buffer zone.
Russia says a number of its troops captured by Kiev’s forces must have accidentally strayed across the border.
President Petro Poroshenko called the vote a “first but very decisive step” toward bringing Ukraine fully into the European Union.
Ukraine had successfully repelled a rebel attack on the government-held Donetsk airport, which came under artillery fire from rebel positions.
Vladimir Putin wants another frozen conflict in eastern Ukraine, says Yatseniuk.
The EU measures, details of which were released on Friday after a preliminary agreement on Thursday.
The sanctions will further curb access to European capital markets for Russian banks and firms.
President Petro Poroshenko said the regions would remain part of Ukraine and rejected the idea of federalisation.
City council of Donetsk said there had been no reported casualties overnight and that public transport would be up and running.
Blasts powerful enough to be heard in downtown Donetsk came from the area near the airport.
A total of 2,000 troops from nine countries – including the US, Canada and Italy – are taking in the exercises.
A separatist leader said this process would begin later on Saturday, though the Ukrainian side said details were still being worked out.