Ukraine's interior minister says Russian forces have taken control of the two main airports in Ukraine's Crimea region, and one report says a Ukrainian coast guard base was surrounded by Russian marines.
Interior Minister Arsen Avakov described the development as a "military invasion" in a Facebook post Friday. He said armed Russian troops were blocking the Belbek airport in Sevastopol, where Russia has a naval base. Unidentified gunmen were also patrolling the international airport in Simferopol, the Crimean capital.
A VOA correspondent who flew into Simferopol Airport on Friday saw gunmen wearing camouflage and carrying automatic weapons at the airport. She described the situation as calm and said flights were still arriving and the airport remained open.
The Associated Press quoted Ukraine's State Border Guard as saying a Ukrainian coast guard base was surrounded by about 30 Russian marines.
Russian state media are carrying statements denying any Russian involvement.
Ukraine's Interim President Olekxandr Turchnyov called an emergency session of his security chiefs Friday to discuss the situation. Ukraine's parliament also urged Russia to to respect its territorial integrity.
The events come a day after gunmen seized control of government buildings in Crimea, a Ukrainian region with strong ties to Moscow. Those gunmen raised the Russian flag over the buildings on Thursday.
Ousted Ukrainian president Viktor Yanukovych, who says he is under Russian protection, was expected to address the media on Friday from the southern Russian city of Rostov-on-Don.
Late Thursday, U.S. Vice President Joe Biden telephoned Ukraine's interim Prime Minister Arseniy Yatsenyuk to welcome the formation of a new government and pledge U.S. support as Ukraine undertakes reforms aimed at restoring the country's economic health. Ukraine's parliament approved Mr. Yatsenyuk, a popular, pro-Western opposition leader, as the head of the interim government earlier in the day.
Mr. Yatsenyuk has accused the Yanukovych government of stealing billions from the state treasury. He said $70 billion in Ukrainian government money had been sent to offshore accounts over the last three years, and that $37 billion of credit it received has disappeared, leaving Ukraine with severe financial problems.
Judicial authorities in Geneva on Friday launched a probe into the allegations of money laundering by Mr. Yanukovych and by his son. The Swiss government has also announced it is freezing the assets of 20 Ukrainian officials.
The International Monetary Fund and European Union are sending teams to Ukraine to assess the country's needs. The United States also is considering $1 billion in loan guarantees.
Also Thursday, the Kremlin sent Russian fighter jets to patrol its border with Ukraine -- a day after announcing large-scale military exercises in the area.
Acting Ukrainian President Turchyno warned that any movement of Russian forces outside their base in the region would be considered "military aggression."
The Crimean parliament voted Thursday to dismiss the regional government and hold a referendum to determine Crimea's status in Ukraine. The referendum is set for May 25, the same day Ukraine will hold a presidential election.