Almost 500 miners are trapped underground after a shell hit an electric substation near the site in war-torn east Ukraine.
Emergency services were alerted when Donetsk’s Zasyadko coal mine, one of eastern Europe’s largest, lost all power in the blast.
It comes just over a fortnight since a similar incident briefly trapped 300 miners on January 11.
A Donetsk region emergencies ministry official said: “When the power went out, there were 496 miners underground.
“But the miners are now making their own way out to safety. The ventilation systems are all working and their lives were never in danger.”
An unnamed separatist “defence ministry” official in Donetsk said 110 miners had been brought back to the ground in the first minutes after the power outage.
It comes as it emerged seven Ukrainian soldiers have been killed in clashes with pro-Russian rebels in the eastern conflict zone over the past 24 hours.
The war between pro-Russian militants and government forces in eastern Ukraine has claimed nearly 5,100 lives since it began nine months ago.
Rebel stronghold Donetsk has seen fighting intensify in recent weeks after a brief lull and the daily casualty figure is again returning to levels last seen at the height of the war in August.
Leaders of the pro-Russian rebels withdrew from peace talks with the Western-backed government in Kiev last week and pledged to seize new territory that could expand their reach over most of Ukraine’s industrial east.
Russia’s President Vladimir Putin accused the Ukrainian army of being “NATO’s foreign legion” whose main purpose was to contain Russia.
“In essence, this is not an army, this is a foreign legion – in this particular case NATO’s foreign legion, which of course does not pursue the objective of serving Ukraine’s national interests,” he said.
“There are completely different goals there.”