they are advancing the most. it has seized its first city kherson and it has encircled mariupol where residents say they are trapped by the shelling. so as we were saying russian has zeroed in on southern ukraine. several cities have been targeted for strategic reasons. controlling the south cuts ukraine off from the sea — and creates a direct link between russia and crimea, which it annexed in 2014. you can see from they're advancing from crimea. these are the latest pictures from mariupol — it's had hours of sustained shelling — hundreds are feared to have died. it's still under ukrainian control — but encircled by russian troops. electricity, water and heat supplies have been cut. authorities say: "they are hindering food supplies, blocking us like in leningrad," — the deadly nazi siege of st petersburg — formerly leningrad — in world war two. they add they're "constantly shelling the city, preventing us from evacuating the injured, and women and children.