Moscow has deployed fighters from Chechnya, known for their ferocity, to wage street battles in Mariupol. Chechnya's Moscow-backed leader, Ramzan Kadyrov, has repeatedly boasted on his messaging app channel about defeating Ukrainians in Mariupol, but the fight has continued.
Boychenko said that several Ukrainian units are still fighting the Russians in Mariupol, including the 36th Marine Brigade, the Azov Regiment, some Interior Ministry troops and border guards.
The Azov Regiment, a seasoned volunteer force that is widely considered one of the country's most capable units, is defending the mammoth Azovstal steel plant that covers an area of nearly 11 square kilometers (over 4.2 square miles). It has taken advantage of the plant's sprawling network of concrete buildings and underground facilities to repel continuous Russian attacks.
The 36th Marine Brigade was maintaining defensive positions at the Azovmash and Zavod Ilyicha factories until it ran out of supplies and ammunition and made a desperate attempt to break through the Russian blockade earlier this week.
In a post on the brigade's Facebook page, one of its officers described the unit's heroic resistance, saying that "for more than a month, the marines have been fighting without replenishing amunition, food and water supplies." "The wounded accounted for nearly a half of the brigade's strength, but those who still had their limbs and were capable of walking reported back to duty," the post said.
Boychenko said that some of the marines managed to join the Azov regiment, while others were captured by the Russians. He didn't give any numbers.
The Russian military said Thursday that a total of 1,160 Ukrainian marines surrendered this week, a claim that couldn't be independently verified.
As the Ukrainian troops continue to offer fierce resistance in Mariupol, fears have grown that the exasperated Russians could resort to chemical weapons to deal with the remaining pockets of resistance at the Azovstal plant and other areas of the city.
Eduard Basurin, a Russia-allied separatist official in eastern Ukraine, appeared to call for that Monday, telling Russian state TV that the Russia-backed forces should block all the exits out of the factory and then "use chemical troops to smoke them out of there." He later said that no chemical weapons were used.
The Azov Regiment claimed Monday, without providing evidence, that a drone had dropped a poisonous substance on its positions but inflicted no serious injuries. A Ukrainian defense official said the attack possibly involved phosphorus munitions.
Boychenko said that an estimated 120,000 of Mariupol's pre-war population of about 450,000 remain in the city.
Ukrainian authorities have said that the Russians have blocked humanitarian convoys from reaching Mariupol, keeping it without food, water and power since the siege started. The Russian troops have turned back buses sent to evacuate residents, but about 150,000 have been able to flee the city in their own vehicles.
Boychenko said that at least 33,500, and, possibly, up to 50,000 Mariupol residents have been taken to "filtration camps" in the separatist-controlled east before being forcibly sent to distant, economically depressed areas in Russia.
Mariupol has seen communications cut since the start of the siege, and as the Russians moved to capture sections of the city they launched radio broadcasts to brainwash the population.
"They unleashed propaganda, telling people that Kyiv and other cities have been captured and they have been abandoned," Boychenko said.
The continuing fighting in Mariupol has forced the Russian military to keep a significant number of troops in the city, delaying the start of the planned new offensive in eastern Ukraine.
"As long as the street fighting is going on, Russia can't remove troops from Mariupol and deploy them to other areas, including Donbas," Oleh Zhdanov, an independent military expert, told the AP.
"The Ukrainian troops in Mariupol are still fulfilling their main task by diverting the Russian forces from other areas. Mariupol remains a major symbol of the Ukrainian resistance."
