Eduard Basurin, the head of the People's Militia of the breakaway pro-Russian Donetsk People’s Republic (DPR), said on Monday that 80 percent of Mariupol’s port has been “liberated” by Russian forces.

"Eighty percent of the port has been liberated, but there’s still resistance," Basurin told Russian state media, according to the Russian state news outlet TASS. "The rest of them are trying to retreat to Azovstal. Azovstal is a fortress within the city."

The southeastern port hub of Mariupol was encircled and besieged by Russian forces in the opening stages of the Russian invasion. The Russian troops resorted to saturation airstrikes against residential areas and reportedly targeted the city’s infrastructure in a bid to force Mariupol’s surrender, giving rise to one of the war’s greatest humanitarian catastrophes.

The Kremlin gave Mariupol’s defenders—composed primarily of the ultranationalist Azov Battalion—an ultimatum in late March to lay down their arms in exchange for safe passage out of the city. “It is you who now have the right to a historic choice—either you are with your people, or you are with bandits, otherwise the military tribunal that awaits you is only a minor thing that you have already deserved because of the despicable attitude towards your own citizens, as well as the terrible crimes and provocations already arranged by you,” said Col. Gen. Mikhail Mizintsev, the head of Russia’s National Center for Defense Management.

Russian forces stormed the city shortly after Kiev and local officials rejected the ultimatum. Within several days of brutal urban combat, Chechen and DPR troops reported that most of the city was under Russian control; the Azov fighters either retreated into the industrial zones of Mariupol’s southernmost port district or continued to hold out in small pockets across residential areas.

The remnants of Azov are believed to be currently holed up in the AzovStal metallurgical plant to the city’s south. According to unconfirmed reports by Russian-language sources, the AzovStal complex features a vast network of underground floors. Azov troops have reportedly bunkered down in these underground levels, which Russian officials say are too fortified to storm. “There are underground floors [at Azovstal], and that’s why it makes no sense to storm this object now,” said Basurin, according to the Kyiv Independent. Basurin suggested that Russia is exploring ways to “smoke” out the Azov battalion, including through the use of chemical weapons. “We could have a lot of our soldiers killed, and the enemy won’t suffer casualties. That’s why currently we should figure out how to block this mill and find all ways in and out. And after that we should ask our chemical forces to find a way to smoke these moles out of their holes,” he said.

Basurin’s comments have sparked concerns among Western governments that Russia could be planning to use chemical weapons in Mariupol. “These reports, if true, are deeply concerning and reflective of concerns that we have had about Russia’s potential to use a variety of riot control agents, including tear gas mixed with chemical agents, in Ukraine,” said Pentagon press secretary John Kirby.         

British foreign secretary Liz Truss said on Monday that London is “working urgently” to verify details of the attack. “Any use of such weapons would be a callous escalation in this conflict and we will hold Putin and his regime to account,” Truss added.

Mark Episkopos is a national security reporter for the National Interest.

Image: Reuters.