Boris Johnson does not want someone in Russia to assassinate Vladimir Putin, Downing Street has said.
Republican US senator Lindsey Graham said on Thursday evening called for the Russian president to be killed.
“The only way this ends is for somebody in Russia to take this guy out. You would be doing your country - and the world - a great service,” he said on Twitter.
Asked if the Johnson agreed, the prime minister’s spokesperson said: “No.
“We stand with the Ukrainian people in demanding the immediate end to the Russian invasion.
“We have said before Putin must be held account in front of an international court for the horrific acts he has committed.”
Anatoly Antonov, the Russian ambassador to the United States, said Graham’s comments were “unacceptable and outrageous”.
“It’s unbelievable that a senator of a country that promotes its moral values as a ‘guiding star’ for all mankind could afford to call for terrorism as a way to achieve Washington’s goals in the international arena,” he said.
It comes after Russian forces shelled a nuclear power station in south-eastern Ukraine, with the attack continuing even as emergency services tried to put out the resulting fire.
Downing Street said the targeting of the nuclear plant could “directly threaten the safety of all of Europe”.
According to the International Atomic Energy Agency (IAEA), the fire did not cause a change in the plant’s radiation level and nor had the shelling or fire caused any damage to “essential” equipment.
The British government has called for an emergency meeting of the United Nations Security Council in light of the attack.