Frustrated Russian forces are prepared to “indiscriminately” use thermobaric bombs to seize control of Ukraine, Western officials believe.
The warning came as Boris Johnson announced that the UK will “imminently” level personal sanctions against Russian President Vladimir Putin and his foreign minister Sergei Lavrov.
One western official said it was “likely” that Russia failed to achieve its main objectives on day one of its invasion of Ukraine.
The official added: “And my fear with those objectives, that timescale not being met, is if that continues to be a theme where they are delayed and then my concern is that that Russia uses indiscriminate use of indirect fire, particularly artillery systems, thermobaric weapons - which we know Russia has both in its armoury and has used in previous conflicts.
“At the moment we’re not seeing the use of those particular weapons. But my fear would be that if they don’t meet the timescales and objectives that they would be indiscriminate in the use of violence and they don’t adhere to the same principles of necessity and proportionality and rule of law that Western forces do.
“I would be very concerned at the attitude they would adopt.”
A thermobaric bomb uses oxygen from the surrounding air to generate a high-temperature explosion, making it more deadly than a conventional weapon.
Meanwhile, western officials also suggested that Russian forces will try to kill Ukrainian president Volodymyr Zelensky and his ministers if they seize control of Kyiv.
One said: “The Ukrainian regime has been characterised by Putin and his spokesperson as Nazis, guilty of genocide, I think today they were described as Nazis and drug takers.
“So it’s clear the kind of vitriol coming from Russia about the Ukrainian leadership so I think we can expect that they would be targets for Russian forces coming into the city.”