German Chancellor Olaf Scholz (SPD) has accused Russia's President Vladimir Putin of a blatant breach of international law and called on him to stop the attack on Ukraine.
"This February 24 is a terrible day for Ukraine and a gloomy day for Europe," Scholz said.
He announced tough sanctions: "The aim of the sanctions is to make it clear to the Russian leadership: It will be paying a bitter price for this aggression. It will become clear: Putin has made a serious mistake with his war…Germany stands by NATO's obligation to provide assistance."
"The situation is serious. The peace in Europe is built on not changing borders. We must return to these principles: State sovereignty is respected. Borders will not be moved," wrote Scholz on Twitter on Thursday morning.
German Foreign Minister Annalena Baerbock warned that the would "not forget this day of shame." She said Russia was breaking "the most elementary rules of the international order." "Germany is stunned, but not helpless," she said, announcing a package of "massive sanctions."
The German foreign ministry put out a tweet reading: "Fighting & missile attacks are taking place in #Ukraine. German citizens are urged to leave the country. If you cannot leave the country by a safe route, stay in a protected place for the time being."
Ukrainian citizens can travel to Germany visa-free to remain in the country for up to 90 days.
Annegret Kramp-Karrenbauer, former defense minister in Chancellor Angela Merkel's previous center-right government admitted policy failures. Taking to Twitter in English on Thursday she wrote she was angry at Germany for not preparing any deterrence and showing military strength.
"This attack will have severe political and economic consequences for Russia," Vice-Chancellor and Economy and Climate Minister Robert Habeck said.
NATO is activating its "defense plans" for allied countries said NATO chief Jens Stoltenberg after a first emergency meeting, he also stressed that NATO would protect its own members, but not move on Ukrainian territory itself.
Russia faces "unprecedented isolation" over its attack on Ukraine and will be hit with the "harshest sanctions" the EU has ever imposed, the bloc's foreign policy chief Josep Borrell said on Thursday morning.
"This is not a question of blocs. This is not a question of diplomatic power games. It's a matter of life and death. It is about the future of our global community," he said in a broadcast statement.
French President Emmanuel Macron said "France strongly condemns the decision of Russia to start a war with Ukraine. Russia must immediately put an end to its military operations."
"In these dark hours, our thoughts are with Ukraine and the innocent women, men, and children as they face this unprovoked attack and fear for their lives," European Union chiefs Ursula von der Leyen and Charles Michel said on Twitter. "We will hold the Kremlin accountable."
The Organization for Security and Co-operation in Europe (OSCE), of which Russia is a member, said "this attack on Ukraine puts the lives of millions of people at grave risk and is a gross breach of international law and Russia's commitments."
Poland, which has a long border with Ukraine has called on NATO to strengthen its eastern flank.
German Interior Minister Nancy Faeser assured Poland and other Eastern European partners "massive support" in taking in refugees from Ukraine.
The president of Romania, Klaus Iohannis, has condemned Russia's "reprehensible" attack on Ukraine and said that Russian President Vladimir Putin "threatens the peace of the entire planet." Romania, a country of 20 million people, borders Ukraine and is preparing to deal with economic and humanitarian consequences that the conflict could generate.
The Baltic nations, Estonia, Latvia, and Lithuania, which gained independence from the Soviet Union only in 1991 and have been members of both NATO and the European Union since 2004 are alarmed.
Lithuania has declared a state of emergency. Latvia's foreign ministry put out a statement saying the country should prepare for "possible security risks."
"Latvia is safe, we are not under a direct military threat," the statement read on Thursday morning and continued that "however, Latvia must also prepare for possible security risks an unpredictable refugee flow, cyber threats, disinformation attacks, and energy resource-related challenges."
UK Premier Boris Johnson took to Twitter to say he was "appalled by the horrific events" in Ukraine.
This article was first published at 9:00 on Thursday, February 24. It is continually being updated as more reactions are coming in.
While you're here: Every Tuesday, DW editors round up what is happening in German politics and society.You can sign up here for the weekly email newsletter Berlin Briefing.