Chinese police have flooded into a depressed mining town near the Siberian border after three days of demonstrations by thousands of unpaid coal miners that posed the first direct challenge to Beijing’s plans to shut mines, steel mills and other lossmaking production.

Hundreds of police from nearby cities cordoned off the city centre of Shuangyashan and plastered the town with posters calling for the capture of at least 75 “criminals” whose faces had been photographed in the crowds during the protests. Workers who took part said many of the organisers were rounded up on Sunday night.

The demonstrations took place during the annual meeting of the National People’s Congress in Beijing, which Premier Li Keqiang has used as a platform to make the case that lay-offs and government funding will be needed to address China’s crippling overhang of unprofitable industrial capacity. Up to 6m people could lose their jobs by some estimates, as Beijing tries to correct for the distortions caused by an excess of state-directed investment and subsidies in the years since the last big restructuring of the state-owned enterprises sector took place between 1998-2001.