Thirteen miners have died and ten were injured after a methane gas fire erupted in a coal mine in the east of the Czech Republic.

It is the worst accident of its kind there in nearly three decades.

The fire broke out at a depth of 880 metres at the CSM mine in the city of Karvina, about 300km east of Prague and close to the Polish border.

"In total, we have 13 dead miners, 12 Polish and one Czech," Ivo Celechovsky, spokesman for the OKD mining company, said.

One of those injured is described as being in a critical condition in hospital.

"Thirteen miners have not made it to the surface. It's impossible for any of them to survive," Polish Prime Minister Mateusz Morawiecki told reporters after visiting the site.

He said that a rescue team had been sent in but that the operation had stopped because of high temperatures in the mine and the danger of further explosions.

Poland's President Andrzej Duda has declared Sunday a day of national mourning.

Mr Celechovsky said the fire was still burning and barriers were being put up to stop it from spreading, with work expected to continue at least until Sunday.

Sympathy poured in as miners lit candles for their dead colleagues at the site and a black flag hung opposite the entrance to the mine.

"It is with great sadness that I learned of the tragic incident in a coalmine in Czechia," said European Commission chief Jean-Claude Juncker.

European Union President Donald Tusk, who is Polish, tweeted that "our thoughts and hearts are with you today."

Czech Prime Minister Andrej Babis called the blast a "huge tragedy" in a tweet, while President Milos Zeman said he was "immensely saddened" by the accident.

Mr Babis also called on OKD to come up with a compensation plan for the affected miners' families, adding the state would step in if the company does not find a way.

Bohuslav Machek, an inspector at the Czech Mining Authority, said the cause of the fire was uncertain.

"There must have been some source, some spark, which ignited the methane," he said.

"There are more possibilities, but at this point it is pure speculation," he added.

OKD, which runs the mine, is controlled by the Czech state.

The accident is the most serious at a Czech mine since 1990 when 30 miners died after a methane explosion at another mine in Karvina.