It comes as Andrzej Duda, Poland’s prime minister, became the first foreign leader to address Kyiv’s parliament in person on Sunday, where he warned the country not to give in to Putin.
Meanwhile, the Ministry of Defence sought to play down advances in Severodonetsk after Russia deployed “Terminator” tank support vehicles in the Donbas region.
And on Monday, Boris Johnson will visit a school where Ukrainian children have enrolled after fleeing the war.
In an open letter to the children of Ukraine, released on Sunday night, Mr Johnson said he was “very sad” to see youngsters absent from the streets and parks of Kyiv when he visited the capital last month, adding: “I cannot imagine how difficult this year must have been for you.”
He wrote: “Since the invasion, many of you have been forced to flee your homes. You have left behind family, friends, pets, toys and all that is familiar, seeking refuge in underground stations, distant cities, even other countries. I cannot imagine how difficult this year must have been for you.”