Air strikes and artillery fire between pro-Russian separatists and Ukrainian troops in the eastern city of Donetsk have brought the violence closer than ever to the city centre as Kiev's forces move in on the rebel stronghold.
With Ukrainian troops encircling Donetsk, western leaders have accused Russia of building up forces along the border in what some fear may preface an intervention.
On Wednesday, Polish prime minister Donald Tusk said he believed that the "the threat of a direct intervention (by Russia) is definitely greater than it was a few days ago, or two weeks ago".
The Donetsk city administration said in a statement published online that three people had been killed in shelling overnight.
In the Kalininsky neighborhood only three miles east of Donetsk's central square, rebels and civilians were milling around outside after a night of what many said they believed were Ukrainian air strikes.
There were eight craters at the scene that appeared to be the result of aerial bombing.
As the Ukrainian military intensified its campaign against the rebels, heavily-populated areas have increasingly come under attack.
Kiev adamantly denies launching artillery barrage and air raids against residential neighboirhoods and accuses the rebels of firing at civilian areas.
Ukrainian security spokesman Andriy Lysenko categorically denied that Ukrainian airplanes have carried out air strikes on Donetsk.
"The cities of Donetsk and Luhansk, as well as other cities and residential areas, are not being bombed by Ukrainian military aviation," Mr Lysenko said.
The Ukrainian government has moved in swiftly on the rebel forces, ousting them from smaller towns in the region and tightening their grip on the regional capital cities of Donetsk and Lugansk.
Donetsk did not see much fighting other than a rebel attempt in May to seize the airport.
But the city has come under more shelling in recent weeks, and local authorities estimate that about 200,000 people in the city of one million have left their homes.
The airport is closed, but buses and trains are still running. The UN has estimated that 1,129 civilians have died in the conflict since April.