Russian forces are reportedly preparing to storm the last major stronghold of resistance inside besieged Mariupol after top Ukrainian officials rejected a demand for the city’s defenders to lay down their arms.

"There are still our military forces, our soldiers, so they will fight until the end and as for now they are still in Mariupol," Ukrainian prime minister Denys Shmyhal told ABC News.

Mikhail Mizintsev, chief of Russia’s National Defense Management Center, released a statement on Saturday demanding that the Ukrainian forces surrender by Sunday morning. "Given the catastrophic situation at the Azovstal iron and steel works, and out of purely humane principles, the Russian Armed Forces offer the militants from nationalist battalions and foreign mercenaries to end hostilities and lay down arms … The lives of all those who lay down their arms will be spared," the statement read.

Citing intercepted radio communications, the Russian Defense Ministry claimed that Kiev “categorically” forbade the city’s defenders—who are vastly outgunned and quickly running out of food and water—from surrendering under any circumstances, adding that any soldiers who do so will be charged with treason and executed.

Ukraine’s rejection of the Kremlin’s ultimatum sets the stage for a final Russian push to eliminate the last pockets of Ukrainian resistance in Mariupol.

The strategic southeastern port hub of Mariupol came under siege in the opening stages of the Russian invasion of Ukraine and has since been nearly leveled by a steady cadence of Russian shelling and airstrikes. Russian forces stormed the city late last month following Kyiv’s rejection of an earlier Kremlin ultimatum for Mariupol’s defenders to lay down their arms in exchange for safe passage. Russian-aligned Chechen fighters and separatist forces from the breakaway Donetsk People’s Republic (DPR) overwhelmed the city, capturing most of Mariupol within several days of fierce urban combat. The city’s remaining defenders, composed largely of the ultranationalist Azov Battalion, retreated southward into Mariupol’s industrial port district.

The last pocket of significant Ukrainian resistance is now concentrated in the Azovstal metallurgical combine. The facility reportedly contains a sprawling network of underground tunnels, considerably reducing the effectiveness of conventional airstrikes. Mykhailo Vershynin, the chief of Mariupol’s patrol police, said on Ukrainian television that the heavily fortified Azovstal plant houses an undisclosed number of local civilians in its plant storage facilities.

Ukrainian officials said the Russian military is set to close off the city on Monday, indicating that further humanitarian evacuations will be suspended until the city is fully under Russian control. Ukrainian foreign minister Dmytro Kuleba said in an interview on Sunday that the situation in Mariupol “may be a red line” in peace talks with Moscow.

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

Image: Reuters