At least seven miners died in a methane gas explosion in a coal mine in Russia's Arctic town of Vorkuta on Monday, the emergencies ministry said on Tuesday.
"The blast struck at 1855 Moscow time (1455 GMT).
According to our information, there were a total of 277 miners underground at the Komsomolskaya mine when it happened," said Emergencies Ministry spokesman Viktor Beltsov.
He said 263 miners had been safely evacuated to the surface and four had been taken to hospital, including one in serious condition.
"The fate of the three missing is unclear," he said.
Methane gas blasts at two coal mines in the Siberian Kemerovo region killed a total of 149 people earlier this year. The accidents were blamed on safety breaches.