Some 170 Polish miners on Wednesday blocked train tracks near the northern border with Russia's Kaliningrad province to stop a train carrying cheaper Russian coal, the border guard service said.
"An approaching train has been stopped before getting to the spot where the miners are," a spokeswoman for the service, Agnieszka Golias, told AFP.
The top government official for the region was heading to the protest site, in the town of Braniewo, Administration Minister Andrzej Halicki told Polish radio.
Russian coal costs less than that mined in Poland, which puts pressure on prices for Polish coal and saps mine revenues. Miners accuse Russia of dumping coal on their market.
Members of the Solidarity union have told Polish media that around 11 million tonnes of Russian coal were imported last years, while five million tonnes of Polish coal were stacked, unsold, by the main mining group Kompania Weglowa.