NATO Secretary General Jens Stoltenberg warned in the ZDF "heute journal" of a further escalation in Ukraine.
The risk is enormous, one is currently experiencing the greatest concentration of military forces in Europe since the end of the Cold War.
Stoltenberg said it was "much more than a maneuver".
Russia has the capacity to invade the neighboring country without warning.
Nevertheless, it is not too late to take a step backwards and find a political solution to the conflict.
Stoltenberg went on to say that they did not want a world order with spheres of influence again, where the great powers decided what their neighbors could or could not do.
And that goes beyond Ukraine.
Stoltenberg emphasised: “We listen carefully to what is coming from Sweden and Finland.
They didn't apply, but they don't want NATO to lock the door if they ever want to get in."
In Ukraine, meanwhile, the Moscow-loyal separatists are calling on civilians to flee to Russia because there is a risk of a military escalation.
First, "women, children and elderly people" should be brought to safety, said the head of the Donetsk separatists, Denis Puschilin, in a speech published on Friday.
"A temporary departure saves you and your relatives' lives." A little later, the car of a high-ranking official apparently exploded in front of the government building in Donetsk, as local media reported.
Nobody was injured.
The background was unclear.
The information cannot be independently verified.
Accusation against the President of Ukraine
The leadership of the self-proclaimed People's Republic of Luhansk also called on people to get to safety.
Russian President Vladimir Putin instructed the government in Moscow to pay the refugees 10,000 rubles (around 116 euros) in emergency aid.
In the Donetsk region alone, 700,000 people are to be brought to safety, it was said in the evening.
The separatists accused Ukrainian President Volodymyr Zelenskyy of wanting to launch a military offensive "in the near future".
The supreme commander of the Ukrainian army, Valeriy Saluschnyj, however, rejected this again in a video message.
"An offensive operation in Donbass inevitably leads to countless civilian casualties, so such scenarios are not even considered," the 48-year-old said.
Kiev wants to solve the conflict peacefully.
"Don't believe the lies of the occupiers," the military said to residents of the separatist areas.
Pushilin, on the other hand, said that combat troops were ready to defend "national territory" against an attack by Ukraine.
Men over the age of 18 were not allowed to leave the country.
"We will win," he said.
Sirens could be heard in videos from Donetsk.
Buses were to take people to shelters in neighboring Rostov Oblast in southern Russia.
People should only take the most necessary things with them, such as documents, money, change items and medicines.
Observers from the Organization for Security and Cooperation in Europe (OSCE) recently noticed a massive increase in exchanges of fire.
Violations of a ceasefire agreed between separatists and government forces have sparked international concern.
According to UN estimates, more than 14,000 people have died in the conflict over the breakaway regions of Luhansk and Donetsk, which has been going on since 2014, most of them in the areas controlled by the separatists.