Anger has spilled over after a mining disaster in Russia that has killed at least 66 workers.
Video footage has emerged of riot police breaking up demonstrations on Friday night by miners demanding better safety measures.
The unrest in the city of Mezhdurechensk came as the rescue effort to find 24 men still missing was called off because of the risk of further explosions.
A day of mourning has been observed in the Kemerovo region where the disaster took place.
This is the same region where 110 people were killed by a methane gas blast in a different mine in 2007.
Observers say safety regulations are often poorly enforced in Russia and fatal accidents are all too common.