(Newsroom America) -- President Barack Obama has warned Russia to pull back from occupying The Crimea, saying any violation of Ukraine's sovereignty would be "deeply destabilizing."
"We are now deeply concerned by reports of military movements taken by the Russian Federation inside Ukraine," President Obama said in a televised statement from the White House.
"...It would be a clear violation of Russia's commitment to respect the independence and sovereignty and borders of Ukraine and of international laws."
He said the United States will stand with the international community in "affirming that there will be costs for any military intervention in Ukraine."
Tensions in the region continue to rise. Armed men are patrolling two airports in Crimea, a peninsula of Ukraine located on the northern coast of the Black Sea.
Ukraine accused Russia of seizing the airports, but Moscow has denied this.
Groups have staged protests, set up roadblocks, and occupied government buildings in several cities throughout Ukraine since November 2013.
The United States is warning it's citizens to defer all non-essential travel to Ukraine, and particularly the Crimean Peninsula, with the State Department issuing a travel warning.
"All U.S. citizens in Ukraine, and those considering travel to Ukraine, should evaluate their personal security situation in light of political instability and the possibility of violence."
Family members of U.S. government personnel were evacuated from Ukraine on February 20 and all Peace Corps Volunteers departed three days ago.
"The Department of State urges U.S. citizens who travel to Ukraine to carefully evaluate the risks posed to their personal safety, particularly in Crimea and the eastern oblasts of Donetsk, Lugansk, and Kharkiv."
While the transition to a new government has been largely peaceful, it said the police presence in Kyiv and other cities remains limited and there is still a potential for violence between supporters of different political parties.
Large crowds remain in Kyiv’s Independence Square and adjacent areas. Since February 27, demonstrations and clashes have occurred in several cities in Crimea and eastern parts of Ukraine.
The State Department warned ground transportation may be disrupted throughout the country. Drivers, especially in Crimea, may encounter roadblocks that restrict access on certain roads.
Commercial air travel could be delayed or cancelled with little or no notice. Travelers should check with their airlines for possible flight delays or cancellations prior to travel.
"The situation in Ukraine is unpredictable and could change quickly. U.S. citizens throughout Ukraine should avoid large crowds. Those in Kyiv should keep away from the downtown areas of Kyiv near Independence Square and government buildings. U.S. citizens should be prepared to remain indoors for extended periods of time should clashes occur in their vicinity," the State Department said.
Protests in Kyiv began on November 21, following the Government of Ukraine’s announcement that it was suspending preparations to sign an association agreement with the European Union.
On February 22, following three months of large protests and violent clashes, former President Yanukovych departed Kyiv, and is believed to be in Russia.
The Ukrainian Parliament established a new government on February 27. Groups that oppose the new government and support closer ties with Russia have staged demonstrations in cities throughout eastern and southern Ukraine.
Unidentified, armed soldiers have occupied several government buildings, including airports, and established roadblocks on the Crimean peninsula and there are media reports that the airspace above the region has been closed and flights cancelled.