Russian forces fired 33 rockets at civilian targets in the Ukrainian city of Kherson in the 24 hours to early Wednesday, Ukraine’s military said, as fighting intensified with Russia deploying more tanks and armoured vehicles on front lines.

The General Staff of Ukraine’s Armed Forces said in its morning report that Russia forces were attacking populated areas on the right bank of the Dnipro River near Kherson with mortars and artillery.

Russia denies targeting civilians. Reuters was unable to immediately verify the reports.

Russian forces abandoned Kherson last month in one of Ukraine’s most significant gains in the 11-month war, but fighting has entered a slow, grinding phase as bitter winter weather has set in.

“There has been very little change in terms of the front line but pressure from the enemy has intensified, both in terms of the numbers of men and the type and quantity of equipment,” said Ukrainian military analyst Oleh Zhdanov.

Zhdanov said that fighting had intensified with Russia deploying armoured vehicles and tanks.

The heaviest fighting has been around the eastern city of Bakhmut, a bombed-out ghost town, which Russia has been trying for months to storm at huge cost in lives, and further north in the cities of Svatove and Kreminna, where Ukraine is trying to break Russian defensive lines.

In Bakhmut, home to 70,000 people before the war and now in ruins, Reuters reporters saw fires burning in a large residential building. Debris littered the streets and the windows of most buildings were blown out.

“Our building is destroyed. There was a shop in our building, now it’s not there anymore,” said Oleksandr, 85, adding he was the only remaining resident there.

Nearby, 73-year-old Pilaheia said she had long got used to the “constant explosions”.

Russian President Vladimir Putin launched his invasion of Ukraine on February 24, calling it a “special military operation” to “denazify” his neighbour, which he said was a threat to Russia.

Russia set out to subdue Ukraine within days, but its forces were defeated on the outskirts of the capital, Kyiv, in the spring and forced to withdraw from other areas in the autumn.

Putin responded by summoning hundreds of thousands of reservists for the first time since World War Two.