The Ukrainian emergency ministry raised the toll from 16 to 18 from an explosion early yesterday at the Sukhodolskaya-Vostochnaya coal mine in the eastern Lugansk region.
Eight miners were still missing today after that blast deep in the mine, likely caused by a buildup of deadly methane gas, while two remained hospitalised with serious burns.
The death toll from a separate accident hours later also rose to seven, and four miners remained missing today after a mine headframe collapsed at the Bazhanova pit in the town of Makiyivka in the neighbouring Donetsk region.
The twin disasters were the country's worst mining accidents since more than 100 miners died in a mine explosion in 2007.
The blast at the Sukhodolskaya-Vostochnaya mine rang out at around 2 am yesterday, in an air passage more than 900 metres deep in the mine, where 28 miners were working at the time, the local emergency ministry said.
Today, "eight miners remained trapped in the disaster zone," the ministry said, without indicating whether they were likely to be alive.
Rescuers were removing gas from an emergency access tunnel into the mine, in order to go down in search of the missing miners, a spokeswoman for the Lugansk regional administration told AFP.
But she said there was little hope of finding more miners alive.
"I can't say anything about this. It is unlikely," said Albina Kosheleva, the Lugansk regional administration spokeswoman.
Two miners pulled from the debris and hospitalised in the city's burns unit remained in "an extremely serious condition, on the verge of life and death," she added. A third survivor died in hospital yesterday.