Now to the crisis overseas one that some fear could pull in the United States. There are fast-moving and mysterious developments on the ground in Ukraine. Who are the armed men taking up position in... See More
Now to the crisis overseas one that some fear could pull in the United States. There are fast-moving and mysterious developments on the ground in Ukraine. Who are the armed men taking up position in the crimea, a region close to Russia and is this the beginning of a Russian invasion? ABC's Alex Marquardt is in crimea with the latest. Good morning, Alex. Reporter: Good morning, Dan, indeed fast-moving and dramatic developments here. You can see some of the pro-russia fervor right here behind me. The pro-russian prime minister says he is in control of the police and army and asked Russian president Vladimir Putin to intervene in crimea, a request the kremlin says it will not ignore. Stoking fears of a major escalation. They are unmistakable, Russian military vehicles, a convoy of Russian Marines now operating on the roads of Ukraine's crimea. A blatant show of force by Russia fueling fears they plan to invade as Ukraine accuses Russia of bringing in thousands of troops. Highly professional pro-russia armed units have taken control of crimea's parliament and airports. These guys are patrolling quietly all around the 5r789. They're not being aggressive. They're not saying anything. And they have no identifying patches, what is clear that they are on the side of Russia and are rejecting the new Ukrainian government. Crimea may technically be a part of Ukraine but culturally and ethnically it is mostly Russian. Crimea did not support the uprising in the capital kiev and many would like to see it become part of Russia. Russia is already in crimea with bases for its black sea fleet and around 15,000 troops. But president Obama on Friday issued a harsh warning against any further military action. The United States will stand with the international community in affirming that there will be costs for any military intervention in Ukraine. Reporter: Russia's actions echoed the buildup to the 200 war with its southern neighbor Georgia. Now Moscow is vowing to defend its facilities and its people in crimea, but has told U.S. Officials it would respect the sovereignty of Ukraine. Even if the Russian military doesn't deploy its own forces, it's clear that its allies already have and are quickly taking control of crimea. So the big question now is how will Ukraine and the rest of the world respond? Bianna. A lot of analysts calling this a global chess match between the two presidents. Our thanks to you, Alex.
This transcript has been automatically generated and may not be 100% accurate.