Why is the Ukrainian city of Bakhmut important to Russia?

Russian and Ukrainian forces are fighting in the streets of Bakhmut - but Russia does not control the eastern city, its deputy mayor has said.

Oleksandr Marchenko also told the BBC the remaining 4,000 civilians are living in shelters without access to gas, electricity or water.

Mr Marchenko said "not a single building" had remained untouched and that the city is "almost destroyed".

Bakhmut has seen months of fighting, as Russia tries to take charge.