Ukrainian security services (SBU) on Monday arrested 43 activists in the country's conflict-ravaged regions.
The group of activists had launched a blockade in January, which effectively disrupted shipments of coal.
Ukrainian nationalists and opposition lawmakers had enforced the blockade, claiming the coal helped fund rebel activities in the region.
"During an operation … in Toretsk, Shtshebryiovka and Kudryumovka, members of the SBU discovered a group of armed men," the Ukrainian army told the country's division of Russia's Interfax news agency.
"They refused to surrender their weapons, which led to the arrest of 43 people," the military spokesman added.
Despite warring parties battling for control of eastern Ukraine, both sides had unusually agreed that the blockade disrupted trade and threatened to cause power cuts.
Many power plants in the area rely on Anthracite coal from rebel areas to keep running, especially during the winter season.
Since conflict broke out in 2014, nearly 10,000 have been killed and more than 500,000 children affected by the fighting, according to UN figures.
Moscow's illegal annexation of Crimea that year, partly in response to pro-European protests that unseated ex-President Viktor Yanukovych, fomented unrest in eastern Ukraine and prompted a pro-Russia insurgency.
The EU on Monday extended sanctions against Russian and Ukrainians individuals for an addition six months after they were first introduced in the wake of the annexation.
The European Council, a body formed of the bloc's political leaders, said it kept sanctions in place "over actions undermining or threatening the territorial integrity, sovereignty and independence of Ukraine."
(AFP, AP, dpa)