The idea, which has animated Ukrainian nationalist circles, is to force the financing of the breakaway regions and their three million or so inhabitants onto Russia’s already weak economy by breaking ties with Ukraine’s industrial base.
“Putin wants us to finance the war he started,” Volodymyr Parasiuk, a member of Parliament and one of the movement’s leaders, said in a telephone interview, referring to the Russian president, Vladimir V. Putin. “He wants the republics to finance themselves, by selling coal.”
The government in Kiev says that the country — western as well as eastern parts — depends on the coal trade for hundreds of thousands of jobs, as well as heat and electrical power.
Already the blockaders have forced a mine and a steel plant in the separatist region to shut down. And economists say half a million jobs and a total of $3.5 billion in revenues from steel exports depend on the coal trains. Some of that money ends up in the coffers of the breakaway regions.
The blockaders say the club-wielding men in the video were thugs hired by the coal industry. Three people were wounded, including one man who suffered a broken leg. Ukrainian government police arrested 37 people, mostly the hired thugs.
It is unclear how many people are involved in the blockade effort. The groups of mostly war veterans are not formally affiliated with any political parties or the government. For a month now, usually armed with hunting rifles and clubs, they have blocked railroad tracks that cross the de facto border into the pro-Russian areas, warming themselves by campfires and shooing away the police.
In their camps along the railway tracks, they wear smudged camouflage and tattered winter coats, like hobos with a geopolitical agenda. At one spot, the men have welded the wheels of a coal train to the tracks, locking it in place and, naturally, preventing other trains from passing.
The war in eastern Ukraine, now entering its third year, has been the bloodiest in Europe since the Balkan conflicts of the 1990s. All the while, however, the lucrative cross-border coal trade has been peculiarly unaffected.
In a remarkable example of big business emerging unscathed from the war, the companies of Rinat Akhmetov, a coal and steel tycoon who is Ukraine’s richest man, have managed to move goods over the border in both directions, without interference from either army. Bloomberg recently estimated Mr. Akhmetov’s net worth at $3.6 billion.
A spokesman for Mr. Akhmetov emphasized the trade was legal and kept people on both sides employed. “We believe that private property is sovereign,” Mr. Akhmetov’s company, SCM Group, said in a statement Thursday.
Reintegrating the separatist regions economically is a requirement of the peace process, known as the Minsk accords, that were signed in February 2015 but never carried out. The agreement also requires that Russia withdraw its unacknowledged military force in Ukraine, referred to diplomatically as the “foreign” force in the region.
On Wednesday, the Ukrainian cabinet tried to defuse the crisis with a decree limiting trade with the enemy to food, medicine and other humanitarian goods, but also coal, recognizing that it is essential for Ukrainian industry.
The interior minister, Arsen Avakov, has condemned the blockade as illegal. But there is little the government can do short of confronting the armed war veterans on the railroad tracks. That is something the government is deeply reluctant to do: Some of the men involved, including Mr. Parasiuk, are still recognized by the public as heroes of the 2014 street fighting that brought President Petro O. Poroshenko to power.
And the movement seems to be picking up political support in Kiev. Aliona I. Shkrum, a member of Parliament with the opposition Fatherland party, said the blockade does not violate international law, in contrast to sieges enforced by the Syrian government against rebel areas there, so long as food and medicine are allowed through, as they are now.
Many of these activists already rue the compromises that Mr. Poroshenko’s government agreed to with Moscow in earlier peace deals, particularly what they see as a commitment to reintegrate the region politically and economically and stage elections before Russian troops leave.
Any potential peace deal with the Trump administration seen as favoring Russia will only aggravate these tensions, inciting more rebellion among a hardened group of protesters.
“Ukrainians have an idealistic idea of resistance,” said Mr. Parasiuk, the member of Parliament who is supporting the blockaders. “If something is wrong, people stand up and resist. The blockade is one example. We don’t have a leader. We have an idea. If you have an idea, you have a movement.”