"There is a requirement that must absolutely be respected -- the territorial integrity of the country," Ayrault told reporters, speaking during a congress of European social-democrats in Rome.
"Everything must be done for this integrity to be totally respected. This requires a great sense of responsibility from all the players, above all from the political forces in Ukraine themselves but also from all of Ukraine's partners," Ayrault said.
"Ukrainians want democracy and we can understand that. They are turning to Europe, to European democracies. It is Ukrainians who must build their future," he said.
French Foreign Minister Laurent Fabius also said that France was "deeply concerned" over reports of significant troop movements in the flashpoint Black Sea peninsula.
"We call on the parties to abstain from actions that could raise tensions and harm Ukraine's territorial integrity," Fabius said in a statement.