Sixteen miners have been killed and another two are feared dead after a methane explosion in a coal mine in the remote Russian Far North within the Arctic Circle.
Two miners were still missing and feared dead on Monday after the explosion at the Vorkutinskaya mine controlled by Russian steel-making giant Severstal in the Komi region town of Vorkuta, the emergencies ministry said.
One of the rescued miners was "in extremely grave" condition, health officials said separately.
A total of 259 miners were working underground at the time, with 23 in the shaft where the explosion took place at the depth of 800 metres.
Five of the group in the shaft were rescued - two received treatment at the scene and three were hospitalised - with the rest either missing or dead.
"Rescue workers found 16 corpses and the fate of two more people is unknown," the emergencies ministry said in a statement, adding that the explosion was caused by methane.
The interior ministry for the Komi region said 18 miners were dead but a Moscow-based spokeswoman for the emergencies ministry refused to confirm that figure before the two missing men are found.
"We are still hoping," Elena Smirnykh, spokeswoman, told AFP news agency, although she admitted they might be dead.
Two of the hospitalised men were in intensive care, one of them in "extremely grave" condition with multiple fractures, injuries and burns, the regional health ministry said, describing the condition of the second man as grave.
The third miner suffered burns to his face.
President Vladimir Putin ordered Vladimir Puchkov, emergency situations minister, to personally go to the mine to oversee the rescue operation.
"The head of state expressed deep condolences to the relatives and loved ones of the killed miners," the Kremlin said in a statement.
The families of the dead miners will receive two million rubles ($66,000) each, Smirnykh, emergencies ministry spokesperson, said.
A plane was dispatched from Moscow to the mine to help with the rescue operation.
Dmitry Medvedev, the Russian prime minister, asked his deputy, Arkady Dvorkovich, with the responsibility to provide assistance to families of the dead miners.
"An accident took place in Komi," a grim-faced Medvedev said in televised remarks. "Put together the complete information and report on what is happening."
The Russian Investigative Committee has opened a criminal inquiry into a possible breach of safety rules at a mine.
'Everybody in shock'
Yevgeny Sukharev, Vorkutaugol spokesman, said the company paid "unprecedented attention" to safety standards.
"Everyone is in shock," he told AFP.
The mine is operated by Vorkutaugol, part of Severstal's coal mining division whose mills it provides with hard coking coal concentrate.
It has been working since 1973 with an output of 1.8 million tonnes of coal a year and its reserves of coal are estimated at 40 million tonnes.
According to the company's website, in 2011 the Vorkutinskaya mine won a corporate award for "worthy working conditions - the basis for respect in the workforce".
Known for its extremely inhospitable climate, Vorkuta was home to one of the most infamous Stalin-era prison camps, the Vorkuta Gulag.
Deadly blasts which are usually caused by a build-up in methane gas remain a frequent occurrence in the coal mining industry in Russia despite recent drives to improve safety.
In 2010, more than 60 people were killed in twin methane blasts at Russia's biggest underground coal mine, the Raspadskaya mine in the Kemerovo region of Siberia.