Coal miners in northern Spain have fired homemade rockets and hurled rocks at police as weeks of protests escalated into violence.
Riot police retaliated with rubber bullets and smoke bombs.
About 200 miners have been on strike in protest against subsidy cuts which unions say will destroy the mines and threaten up to 30,000 jobs.
There have been no reports of casualties from the clashes which took place in the town of Cinera.
A number of towns in the northern Spanish provinces of Asturias and Leon, where mining is a major industry, have seen tens of thousands of protesters take to the streets in recent weeks.
On Tuesday, masked miners set up several barricades on motorways, setting fire to them and blocking the way.
When police tried to remove one of the barricades, some of the protesters fired rockets at them and threw firecrackers.
Protesters also fired makeshift rocket launchers propped from behind wheelie bins.
Last week, several people were injured in clashes, and a rail passenger was injured in Gijon when his train hit logs that police said had been placed across rails by strikers.
The coal mines are dependent on state aid, and Spain's debt-stricken government wants to cut their subsidies from 301m euros (£243m; $383m) to 111m euros, a move unions say will destroy the industry.
The Asturias regional government has condemned the violence, but asked Madrid to rethink its plans.
Spain is grappling with an economic crisis brought on by a collapsed property boom, and currently has the worst unemployment rate in the eurozone.
On Saturday, eurozone ministers agreed to lend Madrid up to 100bn euros (£80bn; $125bn) to help bail out its struggling banks.
The crisis has prompted Prime Minister Mariano Rajoy to impose an austerity drive.