Simferopol, Ukraine (CNN) -- Amid the chaos in Ukraine, an odd standoff played out Sunday at one military base on the country's Crimean peninsula.
Several hundred men, wearing dark green camouflage uniforms without insignia, surrounded Ukraine's Perevalnoye base near the Crimean capital of Simferopol, according to a CNN crew that was there.
But rather than the tense scene one might expect with two forces facing off, the men -- who were on foot and in a dozen or so vehicles -- walked peacefully near 15 Ukrainian soldiers standing guard at the base.
Reporters have walked right up to the men in dark green and asked them who they are, but they have refused to respond. The Ukrainian soldiers are doing the same.
That mood continued amid crowds of civilians who were there to voice their opinions about the chaos that has enveloped Ukraine in recent months, starting with street protests that were sparked by President Viktor Yanukovych's rejection of a trade deal with the European Union. Yanukovych was ousted February 22.
There has been a deepening schism in the country ever since, between those in the west -- who generally support the interim government and its European Union tilt -- and those in the east, who prefer a Ukraine where Russia casts a long shadow.
Emotions are most intense in Crimea, the last major stronghold of opposition to the new political leadership. Ukraine suspects Russia of fomenting tension in the autonomous region that might escalate a bid for separation by its Russian majority.
Kiev mobilized troops and called up military reservists. Russian generals led their troops to three bases in the region and demanded Ukrainian forces surrender and hand over their weapons, Vladislav Seleznyov, spokesman for the Crimean Media Center of the Ukrainian Defense Ministry, told CNN.
Speaking by phone, he said Russian troops had blocked access to the bases.
But, he added, "there is no open confrontation between Russian and Ukrainian military forces in Crimea." He said Ukrainian troops continue to protect and serve Ukraine.
At the base Sunday, pro-Russian protesters chanted on one side of the street, while pro-Ukrainian protesters, including a priest and a man who read aloud from the Bible, rallied on the other. A group of women sang in support with Ukraine. Those who supported Russian intervention marched carrying Russian flags. They sang "Crimea is part of Russia" and recited verses that suggested former Soviet Premier Nikita Khrushchev gave Crimea away, from Russia to Ukraine, in the 1950s without the consent of the people. There was a brief shouting match between the protesters but the peace was maintained.
In the meantime, political rhetoric heated up and Ukraine's leaders foreshadowed more ominous days ahead.
"This is a red alert. This is not a threat," Ukrainian interim Prime Minister Arseniy Yatsenyuk said. "This is actually a declaration of war to my country."
Speaking in a televised address from the parliament building in Kiev, he called for Russian President Vladimir Putin to "pull back his military and stick to the international obligations."
"We are on the brink of the disaster."
U.S. Secretary of State John Kerry blasted what he described as Russia's "incredible act of aggression" during an appearance on CBS's "Face the Nation" on Sunday
Other countries are "prepared to put sanctions in place, they're prepared to isolate Russia economically," he said.
Opinions about what is best for the region are divided.
In Kiev, thousands of people rallied in the central Independence Square, the cradle of Ukraine's three-month anti-government protests that led to Yanukovych's ouster. The crowd held up signs reading "Crimea, we are with you" and "Putin, hands off Ukraine."
At a military base in Crimea, a car carrying Russian troops rolled up early Sunday morning.
They commanded Ukrainian troops to lay down their weapons and mount the Russian flag, Sergei Stichenko, chief of the Central Operative Force of Ukraine's Navy, told Crimean network ATR TV. A Russian captain ordered them to leave.
Stichenko said he refused.
"I told him no one is going to leave the base. Moreover, no one is going to go to the side of the Russian Federation," he said. "We only obey commands from Kiev."
But back at another military base near Simferopol, a 66-year-old man named Nikolai Petukhov marched up to the entrance of the facility carrying a Russian flag. He told CNN that he hoped Putin would facilitate democratic elections in Ukraine.
When asked whether he thinks Crimea should be part of Russia or Ukraine, he said, "If you look at it logically, it should be part of Russia."
Back in the Perevalnoye base, more civilians showed up to join the protest groups. Some women held up signs that said, "God save your people."
A Ukrainian woman named Kseniya spoke to CNN. She was skeptical that a peace would hold for long, of the men in the dark green, she said. They "say they are here to protect us, but who will they protect us from?" she asked.
Waving a Russian flag, Petukhov, a former soldier, insists Crimea is Russian and should return to Russia with Putin's help.
Ben Wedeman and Clare Sebastian reported from Simferopol, Ukraine, and Ashley Fantz wrote from Atlanta. CNN's Samira Said, Mark Morgenstein, Ian Lee and Marie-Louise Gumuchian contributed to this report.