The Russian invasion of Ukraine is likely to become "more violent" as Vladimir Putin's troops are "behind schedule", the Defence Secretary has said.
Ben Wallace said Russian forces were suffering significant casualties and public anger at home, which could lead to a ratcheting up of the horror inflicted on Ukraine.
Mr Wallace warned the Russian handbook pointed to "ruthless, indiscriminate bombing of cities" with "high casualty levels" as the offensive entered its fifth day.
Russian and Ukrainian forces have been engaged in heavy fighting, with Ukrainian President Volodymr Zelensky told Boris Johnson the next 24 hours would be "crucial" in the conflict.
Mr Wallace told BBC Breakfast that Ukrainians were putting up "a very strong fight" but they were going up against "the overwhelming scale of the Russian Federation Army".
He said: "[ Russia ] are behind schedule, they are taking significant casualties and they are feeling public rejection in parts of the Russian system itself; we've seen many protests.
"But the Russian handbook is to then get more violent and commit more forces because fundamentally in the Russian, sort of, doctrine the lives of their own soldiers matter much less than in other armed forces.
"So we have to brace ourselves for what may come next, which could be ruthless, indiscriminate bombing of cities and propelling forward of soldiers and high casualty levels, and that's going to be horrific."
Mr Wallace said President Putin's nuclear threats were part of a "battle of rhetoric" but insisted the UK would take his warnings very seriously.
"We don't see or recognise in the sort of phrase or the status he described as anything that is a change to what they have currently as their nuclear posture," he said.
"This is predominantly about Putin putting it on the table just to remind people, remind the world, that he has a deterrent."
He added: "We will not do anything to escalate in that area, we will not do anything to feed any miscalculation, we take it very, very seriously.
"But at the moment this is a battle of rhetoric that President Putin is deploying, and we just have to make sure we manage it properly."
Mr Wallace distanced himself from a suggestion by Liz Truss that she would support people who wanted to travel to Ukraine to help battle Russian invaders.
The Foreign Secretary faced criticism for backing President Zelensky's call for foreign fighters to join the resistance in Ukraine.
Mr Wallace said Ms Truss was right that it was a "just cause", but told Sky News: "If you're keen to help and you're a United Kingdom citizen, come and join our armed forces."
He said: "Look, there are people who will go... I think what I would say is unless you are properly trained, unless you are a - you know - experienced member of an armed forces, I think there are better ways for you to contribute to the security of Ukraine."
The top Tory also hinted there could be further support for Ukrainian refugees after Boris Johnson was criticised for only offering entry to people with immediate family members in the UK.
Temporary visa exemptions published on Sunday night only apply to spouses, the parents of children under 18 or a child under 18, and close relatives requiring care.
Mr Wallace said the UK "will do everything we can to support the Ukrainians", with more details due later today.
Foreign Affairs Committee chairman Tom Tugendhat said senior ministers had indicated the UK could follow the EU in taking in Ukrainian refugees for up to three years.
Asked whether the UK had gone far enough, the Tory MP told the BBC: "I've been speaking to ministers this morning and I can tell you there are many who are hopeful that this will be something that's reviewed in the coming days."
Asked about the EU's announcement that member countries would grant asylum to Ukrainian refugees for up to three years, Mr Tugendhat said: "I suspect that's likely to be where we end up to be honest."
"I think there's a definite opportunity to be generous," he added.
