Ukrainian President Volodymyr Zelensky has expressed his gratitude to Boris Johnson for supporting his country "from the first day of the Russian terror" after the Prime Minister announced his resignation.
In the Ukrainian leader's nightly video address on Thursday, he said news of Mr Johnson's decision to quit was the "main topic (of conversation) in our country".
Mr Zelensky added that Britain held [holds] a leading global role "in the protection of freedoms" and "the leadership and charisma of the head of state are always of exceptional importance".
In thanking Mr Johnson for supporting Ukraine "from the first day of the Russian terror", Mr Zelensky said: "Whatever is happening in London's rooms of power, Great Britain's support for Ukraine should not change."
The Ukrainian president said when he had expressed his gratitude to Mr Johnson earlier on Thursday as the two spoke by phone, the Tory leader had offered assurances the UK would remain steadfast in its support of the war-torn nation.
Mr Johnson announced his resignation after droves of ministers and Government officials quit over the latest scandal to engulf him, marking an end to three tumultuous years.
The final straw for the leader who took Britain out of the European Union and steered it through COVID-19 and the war in Ukraine was his appointment to deputy chief whip of an MP who he knew to have had sexual misconduct allegations made against him.
This came on top of the scandal over parties at Downing Street, which Boris Johnson was accused of misleading the House of Commons over – and for which he received a police fine.
Another Ukrainian politician has said that people in Ukraine are "concerned" after Boris Johnson's resignation as Tory leader.
Watch: How big a role has Boris Johnson played in the Ukraine conflict?
The Prime Minister's handling of the row over scandal-hit former deputy chief whip Chris Pincher prompted Tory MPs to abandon him and leave him with no choice but to resign.
Deputy leader of the Holos Party Inna Sovsun told the PA news agency: "Over in Ukraine people are very much concerned.
"I understand that there are different assessments of Boris Johnson himself and people look at him very differently, but we in Ukraine, now, look at different Western politicians from a single standpoint: the level of support to Ukraine.
"We don't have the luxury to debate anything else, except for that. And in that sense, Boris Johnson has, of course, been a great friend to Ukraine.
"He was really driving the support, the political support, for the country. He was very outspoken, he was always on Ukraine's side.
"We are very much worried if this policy of the UK Government will continue."
Ms Sovsun added that she hopes the decision as to who will take over from Mr Johnson "will be made soon".
She said: "We are ready and willing to work with whoever that will be, and will do everything in our power to work with the next prime minister.
"We hope the decision will be made soon and we will be able to continue this fruitful cooperation in military and other affairs as well."