Ukrainian police officers have returned – along with TV and radio services – to the southern city of Kherson following the withdrawal of Russian troops.

The deployment is part of fast-but-cautious efforts to make the only regional capital captured by Russia habitable after months of occupation. One official has described the city as “a humanitarian catastrophe”.

People across Ukraine awoke from a night of jubilant celebrating on Sunday after the Kremlin announced its troops had withdrawn to the other side of the Dnieper River from Kherson.

The Ukrainian military said it was overseeing “stabilisation measures” around the city to make sure it was safe.

The Russian retreat represented a significant setback for the Kremlin some six weeks after President Vladimir Putin annexed the Kherson region and three other provinces in southern and eastern Ukraine – in breach of international law – and declared them Russian territory.

About 200 officers were at work in the city, setting up checkpoints and documenting evidence of possible war crimes. Police teams were working to identify and neutralise unexploded ordnance.

Ukraine’s communications watchdog said national TV and radio broadcasts had resumed and an adviser to Kherson’s mayor said humanitarian aid and supplies had begun to arrive from the neighbouring Mykolaiv region.

But the adviser, Roman Holovnya, described the situation in Kherson as “a humanitarian catastrophe”. He said the remaining residents lacked water, medicine and food — and key basics such as bread went unbaked because of a lack of electricity.

“The occupiers and collaborators did everything possible so that those people who remained in the city suffered as much as possible over those days, weeks, months of waiting” for Ukraine’s forces to arrive, Holovnya said. “Water supplies are practically nonexistent.”