Images shared with news agencies late on Friday appear to show a Ukrainian Black Hawk helicopter deploying about 10 troops near Pokrovsk, although the location and date could not be verified.
Russia’s defence ministry said it had thwarted the deployment of Ukrainian military intelligence special forces north-west of the town, killing all 11 troops who landed by helicopter.
DeepState, a Ukrainian open-source monitoring group, estimates about half of Pokrovsk is a so-called “grey zone” where neither side is in full control.
A military source in Donetsk told the BBC that Ukrainian forces were not surrounded but their supply lines were under fire from Russian troops.
The US-based Institute for the Study of War said Ukrainian forces had “marginally advanced” during recent counter-attacks north of Pokrovsk, but said the town was “mainly a contested ‘grey zone'”.
Moscow wants Kyiv to cede the Donetsk and the neighbouring Luhansk regions (collectively known as Donbas) as part of a peace deal, including the parts it currently does not control.
Russia launched a full-scale invasion of Ukraine in February 2022, and currently controls about 20% of Ukrainian territory, including the Crimean peninsula Moscow annexed in 2014.
Pokrovsk is a key transport and supply hub whose capture could unlock Russian efforts to seize the rest of the region.
But Kyiv also believes its capture would help Russia in its efforts to persuade the US that its military campaign is succeeding – and, therefore, that the West should acquiesce to its demands.
Washington has grown increasingly frustrated with the Kremlin’s failure to move forward with peace negotiations – culminating in US President Donald Trump placing sanctions on two largest Russian oil producers and axing plans for a summit with President Vladimir Putin.
Zelensky has publicly agreed with Trump’s proposal for a ceasefire that would freeze the war along the current front lines.
Putin is refusing to do so, insisting on his maximalist pre-invasion demands that Kyiv and its Western allies see as a de facto capitulation of Ukraine.
Additional reporting by Jaroslav Lukiv
