At least 32 miners were killed on Wednesday in a blast at a coal mine in a rebel-held area of eastern Ukraine, a senior politician and a mining union spokemsan said.
The blast took place near the bombed-out shell of Donetsk airport.
The city has been the focus of a nearly year-long conflict between government forces and pro-Russian rebels.
"A terrible tragedy took place this morning at Zasyadko (mine). There are victims, currently numbering 32," Volodymyr Groysman, chairman of the national parliament told the assembly in Kiev, calling on lawmakers to observe a minute's silence.
Mykola Volynko, head of the Miners' Union of Donbass, which covers the eastern region, confirmed the toll.
"At the moment we know of 32 people dead. We don't know how many people are still in the mine," he told AFP.
A spokeswoman for the ministry of emergency situations of the self-proclaimed Donetsk People's Republic told AFP there were still scores of people in the mine.
"At the moment there are still 70 people underground but the situation is constantly changing as we bring people to the surface," spokeswoman Julia Bedilo said, blaming the blast on trapped methane gas.
The accident comes nearly three weeks into a ceasefire deal which has held for the most part.
A spokesman for Ukraine's Independent Miners Union, Mikhail Volynets, said 207 miners were underground at the time of the incident, with 53 in the part of the mine rocked by the explosion.
Ukraine's coal mines are considered among the world's most dangerous, with many of them poorly financed and employing outdated Soviet-era equipment.
Zasyadko mine, which is owned by Yukhym Zvyahilsky, a member of the national parliament, is one of the most notorious.
In 2007, the site witnessed the worst accident of its kind in the country's post-Soviet history, when 101 miners were killed in a blast. Most of the country's mine disasters are caused by build-ups of methane gas.