Ukrainian planes and artillery have bombarded separatist positions as residents fled the city of Donetsk. President Petro Poroshenko has vowed to punish rebels who launched a deadly rocket attack on government forces.
Artillery fire from the Ukrainian army was also said to have hit four apartment blocks near a separatist base in the Donetsk suburb of Maryinka.
Russian-born separatist commander Igor Girkin, also known by his nom de guerre Strelkov, told the Interfax news agency that there had been some 30 civilian deaths in the latest offensive. He added that militants were withdrawing from sites that had come under attack.
Stelkov denied a Ukrainian government report that at least 500 separatists had been killed in air strikes near the town of Dzerzhinsk, saying that the garrison had left the area ahead of the strikes.
On Friday, Ukrainian President Petro Poroshenko said that he would find and destroy the rebels responsible for an attack at Zelenopillya, where at least 23 people were killed by separatists using Grad missiles.
The industrial city of Donetsk was described by the AFP news agency as a "ghost town," and the roads outside of it were said to be filled with refugees.
Anxiety over possible siege
The exodus began as the leaders of the self-styled Donetsk People's Republic announced that they would evacuate whole neighborhoods in anticipation of a possible siege by forces loyal to Kyiv. However, some residents said they were fleeing out of fear that they would by used as human shields by the separatists.
"The militia has begun blowing up roads, so I want to get out while there is still time. I don't want to turn into a living shield for the militants," businessman Andrei Koziyatko told the AFP news agency.
Some 70,000 people had already fled by Friday, according to Donetsk People's Republic leader Aleksandr Borodai, who said the number was still rising.
Meanwhile, on Saturday, the European Union targeted Ukrainian separatist leader Borodai and 10 other individuals with travel bans and asset freezes, in a widening of their existing blacklist.
An EU statement called Borodai "responsible for the separatist activities of the so-called 'government of the Donetsk People's Republic'." Others on the list included Khodakovsky, a defector from the Ukrainian state security service
rc/mkg (AFP, dpa, Reuters)