Protesting Polish farmers on tractors have blocked major roads leading into Warsaw as thousands of supporters gathered in front of the Prime Minister’s office.

Some trampled a European Union flag and burned a mock coffin bearing the word “farmer”.

The protesters are demanding a withdrawal from the EU’s Green Deal, a plan meant to fight climate change with measures that farmers denounce as excessively costly.

They also want the Polish-Ukrainian border closed to stop the imports of Ukrainian food products.

Such protests have occurred across the 27-member EU, but this one seemed to be angrier than earlier demonstrations in the central European nation.

Farmers were joined by miners, foresters, hunters and other supporters. They blew horns and set off firecrackers and smoke bombs, despite police warnings that the use of pyrotechnics was banned. Some protesters burned tyres.

The protest increased the pressure on the government of Prime Minister Donald Tusk, a former president of the European Council who is strongly pro-EU and seeks to support Ukraine as it fights Russia’s invasion.

Mr Tusk has sought to meet the farmers’ demands, calling their frustrations justified. He has said he plans to propose amendments to the Green Deal.

He said this week: “Environmental protection cannot and does not have to be in conflict with food production.”

Mr Tusk is also trying to address the anger caused by an influx of Ukrainian grain and other food, which Polish farmers say drive down market prices and put Poland’s agricultural sector in jeopardy.

They seek a ban on the Ukrainian imports and are angry at the EU for lifting tariffs on them while Ukraine – a major food producer – sought ways get its food to global markets.

Despite Mr Tusk’s overtures to farmers, the protest had a strongly anti-government feeling, with slogans on some posters denouncing him.