John Ratcliffe travelled to the Russian capital on Tuesday in a rare and unannounced visit.
Fuel companies are urging customers not to linger at the pumps after a wave of deadly attacks.
The comments on BBC Newsnight come after the UK announced it has agreed to hand over blueprints for British-made missile components to Ukraine.
It comes after Moscow warned of "consequences" over the reported use of British drones by Ukraine.
The BBC's Joe Inwood breaks down the weapons technology that could make a difference in the Russia-Ukraine war.
Bradley Townsend left South Yorkshire in April, telling his family he was going to Romania.
Correspondent Joe Inwood breaks down the weapons technology that could make a difference in the Russia-Ukraine war.
Burnham promises to keep up the pressure on Russia despite Moscow's "outrageous threats," on his first official visit to Ukraine as UK prime minister.
UK Prime Minister Andy Burnham is handing over blueprints so Kyiv can build its own long-range missiles.
New figures show that ever since the Ukraine war, net migration to the Republic of Ireland has steadily decreased.
Ozon says its warehouses across southern Russia, including in Dagestan and Krasnodar, were hit in the overnight strikes.
Boris Johnson, Rishi Sunak, Keir Starmer and Andy Burnham have all visited Ukraine's capital since 2022.
