The World Health Organization's European head said on Thursday that the body was preparing for possible "chemical assaults" in Ukraine.
"Given the uncertainties of the current situation, there are no assurances that the war will not get worse," Hans Kluge, WHO regional director for Europe, said in a statement sent to journalists from Lviv, Ukraine.
"WHO is considering all scenarios and making contingencies for different situations that could afflict the people of Ukraine, from the continued treatment of mass casualties, to chemical assaults," he said, without providing further details.
Western officials have repeatedly voiced fears that Russia may use chemical and biological weapons in Ukraine, with risks of spillover effects beyond the country.
Russia's defence ministry has accused Kyiv, without providing evidence, of planning a chemical attack against its own people in order to accuse Moscow of using chemical weapons in the invasion of Ukraine that began on Feb. 24.
In the same speech, which was delayed due to an air raid siren in Lviv, Kluge said the WHO was coordinating with the European Union to triage patients arriving from Ukraine and arranging for them to be sent on for treatment within Europe.
He said that the WHO has already delivered over 185 tonnes of medical supplies including material to support trauma across Ukraine and said a further 125 tonnes were on the way.
A WHO database showed that there have been 91 attacks on Ukraine's health care infrastructure resulting in 73 deaths since the invasion began, without saying who was responsible.