Ukraine's southern city of Mariupol is at risk of a major cholera outbreak as medical services are likely already near collapse, Britain's defence ministry said on Friday.

There is likely also a critical shortage of medicines in Kherson, Britain's Ministry of Defence said in a Twitter update.

Russia is struggling to provide basic public services to the population in Russian-occupied territories, it added.

Last month, WHO's Ukraine Incident Manager, Dorit Nitzan, said Mariupol, which is now controlled by Russian forces after weeks of siege and heavy bombardment, was among occupied areas where there was a risk of cholera.