In the letter to Mr Kelin, Mr Robertson called for an immediate end to the conflict and demanded that all Russian troops withdraw from Ukraine immediately.
His letter comes two days after UK Foreign Secretary Liz Truss summoned the Russian ambassador to condemn the attack on Ukraine. She told Mr Kelin that Russia had repeatedly lied about having no plans to invade Ukraine, and its unprovoked aggression had made it an international pariah.
Mr Robertston said: “The Scottish Government condemns Russia’s unprovoked invasion of a peaceful, democratic neighbour in the strongest possible terms. We call for an immediate cessation of Russia’s aggression and demand that all Russian troops withdraw from Ukraine immediately.
“This illegal act of aggression has no conceivable justification. I reject wholeheartedly the premise of the invasion as stated by President Putin. I deplore the loss of life, including civilian lives, which is the direct responsibility of the Russian regime.”
Mr Robertson said that the invasion follows a “pattern of aggression and belligerence”, but insisted that Scotland’s quarrel “is not with the people of Russia” or the Russian community in Scotland.
He said: “Scotland offers its unqualified support for Ukrainian sovereignty, independence and territorial integrity. Our capital city Edinburgh is twinned with Kyiv, and our country is home to several thousand Ukrainians who are valued and welcome members of our communities.
“Scotland is also home to many Russians, whom we value equally. They are our friends, family, co-workers and neighbours. Our quarrel is not with the people of Russia, nor the Russian community who live and work in Scotland, but with President Putin’s regime and its deplorable actions.”
He added: “Mr Ambassador, history will judge this week’s events as a permanent stain on this Russian government’s reputation. The international community stands united against such aggression, and Scotland stands with the international community.”