Ukraine's energy grid has been badly hit after weeks of massive Russian attacks. Photo: AFP
Ukraine has condemned unsubstantiated claims by Russia that Kyiv might use a "dirty bomb" - conventional explosives laced with radioactive material.
President Volodymyr Zelensky said this meant Russia itself could be preparing an attack of this kind.
Ukraine's allies also dismissed the claims, with the US saying it "rejected any pretext for Russian escalation".
Russian Defence Minister Sergei Shoigu made the dirty bomb remarks in a call with his UK counterpart Ben Wallace.
He said he was "concerned about possible provocations by Kyiv involving the use of a dirty bomb".
On Sunday, Shoigu also held a flurry of phone calls with defence ministers of the US, France and Turkey, voicing Moscow's alarm. He provided no evidence to back up his accusations.
Responding to this, President Zelensky accused Russia of being "the source of everything dirty that can be imagined in this war".
He said Russia was threatening the world "with a radiation disaster" at the Zaporizhzhia nuclear plant which it had captured and also spoke of Moscow's threats to detonate a major dam in southern Ukraine. The Kremlin denies the allegations.
The Ukrainian leader also stressed that "the world should react in the toughest possible way".
Meanwhile, Wallace said he refuted Shoigu's allegations that "Ukraine was planning actions facilitated by Western countries, including the UK, to escalate the conflict in Ukraine".
He also cautioned that such claims "should not be used as a pretext for greater escalation".
Similar comments were made by the US Secretary of Defence, Lloyd Austin, who spoke to Shoigu on Sunday, in what was the second such phone call in days.
Military analysts note that the Russian accusations come after a string of heavy Russian military defeats and as Ukrainian troops continue their counter-offensive operations in the east and south of the country.
The US-based Institute for the Study of War (ISW) said in a series of tweets that Shoigu "likely sought to slow or suspend Western military aid to Ukraine and possibly weaken the Nato alliance in scare-mongering calls".
However, the ISW added: "The Kremlin is unlikely to be preparing an imminent false-flag dirty bomb attack. Shoigu's claims further a longstanding Russian information campaign."
- BBC