By Adam Easton
BBC correspondent in Warsaw
Thousands of Polish coal miners have begun a protest against government plans to restructure the loss-making industry.
This is the latest in a series of miners' protests
Waving the red and white flags of the Solidarity trade union, miners marched peacefully across main roads in the industrial heartland of Silesia, bringing traffic to a standstill.
They're calling it the total blockade of Silesia.
Poland's miners are furious the government is unwilling to discuss its decision to close four pits in the area next year.
Talks between workers and the state coal company's management broke down earlier this week.
The demonstration is the latest in a series of protests, which turned violent earlier this month during a huge rally in Warsaw.
Angry miners threw rocks and Molotov cocktails, while police responded with tear gas and water cannon.
Dozens of policemen and miners were injured.
Miner's leaders hope their firm stance will force Poland's unpopular Social Democrat government to back down.
It may yet do so.
High unemployment is one of the biggest problems facing a government already plagued by corruption scandals.
Some estimates put the number of jobless in Silesia at twice the national rate of 18%.
But Poland's coal industry - the second largest in Europe - is heavily in debt - to the tune of $6.5bn.
To make it more efficient and receive much needed World Bank funds, the government wants to cut costly production and shed 14,000 jobs.
And when Poland joins the European Union next May the government knows it will no longer have free rein to bale out the ailing coal sector.