Kyiv has even ordered “very audacious” attacks on Russian soil to further hamper Moscow’s preparations, an analyst said.
Justin Crump, of Sibylline, an intelligence and geopolitical risk firm, said: “Ukraine appears not only to be operating on Russian territory but also conducting very, very audacious operations there, including blowing up bridges and destroying supply dumps.”
An intelligence briefing by the UK’s Ministry of Defense said Russia’s failure to capture the besieged port city of Mariupol had also slowed Moscow’s advances elsewhere in Ukraine.
“Russian commanders will be concerned by the time it is taking to subdue Mariupol,” it said.
“Concerted Ukrainian resistance has severely tested Russian forces and diverted men and material, slowing Russia’s advance elsewhere.”
Mariupol is seen as another crucial strategic area by the Kremlin because its capture would create a land bridge between Crimea and Russia.
Ahead of its anticipated attack on eastern Ukraine, Russia stepped up its bombardment of civilian targets across the country.
Scores were reported dead after missile attacks on Kyiv and Lviv, as well as shelling in the city of Kharkiv.