The only place in Mariupol where there are any troops remaining is in the catacombs under the giant, sprawling steel plant, Azovstal. And the ring containing them keeps getting tigher and tigher.
This is incredible war footage, but I think it's also fair to describe it as Russian propaganda, given what little one can surmise about the source. RUSSIAN MARINES AND DPR STORMING AZOVSTAL OUTSKIRTS
President Putin made a speech where he ordered that the remaining Ukrainian military troops be blockaded, but that the Russian forces not assault the plant and try to clear the tunnels, corridor by corridor. To prevent the death and injury of many Russian troops fighting in the tunnels would result in.
The rest of the city appears to be under Russian control, as evidenced by the many recent videos posted on line.
It's a very grim situation for the fighters in the tunnels, estimated at about 1,000 men. They are totally cut off and can't get resupply. They are disinclined to surrender because the majority of the force is the Azov (sometimes spelled Azoff, Asof, etc.) Brigade, which is the voluntary far-right (in Ukrainian terms) militia which helped overthrow the elected government in 2014, and has taken the lead in attacking the break-away republics in the Donbas.
They are who President Putin and the Russians refer to as "Nazis" (not a completely arbitrary claim, as there are direct links from the current Azov leaders and the Nazi Occupation Government of Ukraine, which unlike Poland, (but like France) had a strong Nazi collaborationist movement.
Unlike France, they did not have a national reckoning with their collaborationists after the end of WW2. Ukraine moved seemlessly into the Soviet Union, and so didn't have the sorts of trials and reckoning with collaborators that France had. Mostly they were allowed to merge back into Ukrainian society. They went on to form "ultra-nationalist" faction and the Azov fighters come directly from those groups.
The Azov Battalion logo on the Left, the Nazi 2nd SS Panzer Division Das Reich (1939–1945), in center. On right the "sun wheel". The background on the Azov logo is a common European White Nationalist logo, the "sun wheel" or "black sun".
When the Azov Battalion surrender they have little to look forward to. They have been promised War Crimes Trials in Russia, probably followed by life in prison in Siberia for most of them. (Russia currently has no death penalty, but it could be reinstated for these fellows, so hated are they in Russia.)
So, the plan is to starve them out. I guess their plan is that somehow the fortunes of the Ukrainian forces reverses, and they are rescued or allowed safe passage as part of a negotiated settlement. Both seem highly unlikely.
This video is unpleasant, but shows the reality of life underground in the steel plant tunnels: