Justin Crump, of Sibylline, an intelligence and geopolitical risk company, said: “Ukraine seems not only to be operating on Russian territory, but also to carry out very, very daring operations there, including the blasting of bridges and the destruction of landfills.” A briefing from the UK Department of Defense said Russia’s failure to seize the besieged port city of Mariupol had also slowed Moscow’s advance into other parts of Ukraine. “The Russian commanders will be worried about the time it will take to subdue Mariupol,” he said. “Coordinated Ukrainian resistance has severely tested Russian forces and diverted men and material, slowing down Russia’s advance elsewhere.” Mariupol is considered another critical strategic area by the Kremlin because its occupation would create a land bridge between Crimea and Russia. Ahead of its impending attack on eastern Ukraine, Russia has stepped up its bombardment of civilian targets across the country. Dozens were reported dead after rocket attacks in Kyiv and Lviv, as well as bombings in the city of Kharkiv.