The UK supports Ukraine's right to strike Russian territory using Western supplied weapons, a defence minister has said.
James Heappey said it was "completely legitimate" for Kyiv to targeting Russia supply chains that contribute to "death and carnage on Ukrainian soil".
He added that the weapons the West - including the UK - is giving to Ukraine "have the range to be used over the border" into Russia.
"The fact is that Ukraine was a sovereign country that was living peacefully within its owner borders and then another country decided to violate those borders and bring 130,000 troops across into their country," he told Times Radio on Tuesday.
“That started a war between Ukraine and Russia, and in war Ukraine needs to strike into its opponents depth to attack its logistics lines, its fuel supplies, its ammunition depots, and that’s part of it.”
He added it is “not necessarily a problem” if British-donated weapons are used to hit sites on Russian soil after accepting that weapons now being supplied by allies to Ukraine have the range to be used over borders.
“There are lots of countries around the world that operate kit that they have imported from other countries, when those bits of kit are used we tend not to blame (the country) that manufactured it, you blame the country that fired it," he said.
It has now been 62 days since Vladimir Putin ordered his troops to invade Russia, causing over five million people to flee Ukraine in search of safety.
Western intelligence suggested Putin expected to have control of the country within a matter of days, but more than two months later his troops have been forced out of the north and reportedly suffered huge losses.
Russia has not put out an exact figure of how many soldiers have died since the beginning of the conflict.
Ukrainian authorities have estimated more than 21,000 Russian soldiers have so far been killed.
On Monday, Russian defence minister Sergei Lavrov said there was a "real danger" of the conflict slipping into a third world war, and said Russia viewed Nato as being “in essence” engaged in a proxy war as sovereign nations are supplying Ukraine with weapons.
Lavrov claimed Russia was striving to prevent nuclear war as they continued the invasion.
"This is our key position on which we base everything," he said on Monday.
"The risks now are considerable. I would not want to elevate those risks artificially.
"Many would like that. The danger is serious, real. And we must not underestimate it."
But his claim shows Russia “senses defeat in Ukraine,” his Ukrainian counterpart Dmytro Kuleba said
He said: "Russia loses last hope to scare the world off supporting Ukraine.
"Thus the talk of a ‘real’ danger of WWIII. This only means Moscow senses defeat in Ukraine.
"Therefore, the world must double down on supporting Ukraine so that we prevail and safeguard European and global security."