Ukraine war: Russians slowly take ground around Bakhmut

"Stay close to the wall. Move fast. Single file. Just a few at a time."

The staccato instructions come from the Ukrainian army escort taking us to a military position in battle-scarred Bakhmut, a city once famed for its sparkling wines.

Ukraine's President Volodymyr Zelensky has called the eastern city "our fortress". Russian forces have spent the past six months trying to capture Bakhmut. Now they have intensified their onslaught - Ukraine believes - to tear it down ahead of the anniversary of the invasion.

We follow orders, darting down an icy rubble-strewn street, with a clear blue sky overhead - ideal for Russian drones.

Just after we cross the road, two Russian shells come slamming down behind us on the other side. We turn around to see black smoke rising and keep on running.

Was the shelling random or aimed at us? We can't be sure, but everything that moves in Bakhmut is a target - soldier or civilian.

For hours there is no let-up in the shelling, incoming and outgoing. A Russian fighter jet roars overhead. The nearest Russian troops are just two kilometres away.

There is street fighting in some areas, but Ukrainian forces still hold the city - despite sub-zero temperatures and dwindling ammunition.