Thousands of Ukrainians gathered in Kyiv's Independence Square Sunday calling for unity, a day after Russian forces seized the last major Ukrainian military base in Crimea.
The rally participants gathered to hear pro-Ukraine speeches, display flags, and place flowers at the site of a makeshift memorial to anti-government protesters who died late last month in clashes with police.
In the eastern city of Donetsk, pro-Russian protesters gathered around an administration building, calling for the resignation of the local governor, who is loyal to Kyiv.
Meanwhile, NATO's top commander addressed the situation in a speech in Brussels. U.S. Air Force General Philip Breedlove, NATO Supreme Allied Commander, said Russia has used snap military exercises as an excuse to amass its troops along the Ukrainian border.
He said NATO has been trying to make Russia a partner, but added that Russia is now acting more like an adversary.
But in Russia, Deputy Defense Minister Anatoly Antonov told Russian news media that Russia is complying with international troop limits near the Ukrainian border.
Germany's Foreign Minister Frank-Walter Steinmeier said after visiting Ukraine this weekend that he fears Russia may have opened "Pandora's Box" with its attempt to redraw national borders in Europe.
"I'm very worried the unlawful attempt to alter recognised borders in our European neighbourhood, 25 years after the end of the Cold War, will open Pandora's Box," Steinmeier told the Welt am Sonntag newspaper in an interview published on Sunday.
"We can't overlook the fact that Russia, with its action in Crimea, is flouting the central foundations of the peaceful order in Europe," he said.
Ukraine has been in political uproar since November, when then-Prime President Viktor Yanukovych backed off of signing a trade agreement with the European Union in favor of closer ties with Russia. The move led to the ouster of Yanukovych and last week's vote by Crimeans to join the Russian Federation, a decision quickly accepted by Russian President Vladimir Putin.
On Saturday Russian troops fired shots and used armored vehicles to smash through the gates of Belbek air base. Ukrainian forces offered no resistance. They sang their country's national anthem before putting their weapons into storage.
At least one Ukrainian soldier was wounded. Some reporters and cameramen covering the takeover were roughed up by Russian soldiers and had their equipment seized, including those working for VOA.
Russian forces also took over a Ukrainian naval base in Novofedorovka.
British Foreign Secretary William Hague, writing in the Telegraph newspaper, said Britain and its allies must be ready for different relations with Russia than what they have enjoyed during the last 20 years. Hague said this would include restricting military cooperation and arms sales to Russia.
In Kyiv Saturday, UN Secretary-General Ban Ki-moon praised Ukraine's interim prime minister, Arseniy Yatsenyuk, for his "real leadership." Ban said he admired the prime minister's call for "inclusiveness and reconciliation."
Meanwhile, Republican U.S. Senator Kelly Ayotte is leading a congressional delegation on a visit to Kyiv Sunday. Ayotte has called for more U.S. aid to Ukraine.