WASHINGTON (AP) -- President Barack Obama is warning Russia there will be costs if Russia intervenes militarily in Ukraine.
Obama says the U.S. is deeply concerned by reports of military movements by Russia inside Ukraine.
He says any violation of Ukraine's sovereignty and territorial integrity would be destabilizing. He says it would violate Russia's commitment to respect Ukraine's borders and would invite global condemnation.
US President Barack Obama speaks about the situation in Ukraine in the briefing room of the White House on February 28, 2014 in Washington. Obama said he was 'deeply concerned' by reports of Russia military in Ukraine. AFP PHOTO/Brendan SMIALOWSKI
Obama says the U.S. stands with the world community to affirm there will be costs for an intervention.
Obama spoke at the White House late Friday.
Meanwhile, a spokesman for the Ukrainian border service says eight Russian transport planes have landed in Crimea with unknown cargo.
Serhiy Astakhov tells The Associated Press that the Il-76 planes arrived unexpectedly Friday and were given permission to land, one after the other, at Gvardeiskoye air base, north of the regional capital, Simferopol.
Unidentified armed men patrol outside of Simferopol airport, on February 28, 2014. Ukraine accused today Russia of staging an 'armed invasion' of Crimea and appealed to the West to guarantee its territorial integrity after pro-Moscow gunmen took control of the peninsula's main airport. AFP PHOTO / VIKTOR DRACHEV
Astakhov says the people in the planes refused to identify themselves and waved off customs officials, saying they didn't require their services.
Earlier Friday, Ukraine's U.N. ambassador said he had told the U.N. Security Council that Russian military helicopters and transport planes are entering his country and that Russian armed forces seized Crimea's main airport.
Russia's Interfax agency cited Serhyi Kunitsyn, a Ukraine presidential envoy to Crimea, telling ATR television that 13 Russian planes carrying 150 Russian troops each landed at Gvardeiskoye air base. That report could not be confirmed
Ukraine's fugitive president resurfaced in Russia to deliver a defiant condemnation of a "bandit coup," while Russian armored vehicles bearing the nation's tricolor rumbled across Crimea and men described as Russian troops took position at airports and a coast guard base - ominous signs of Russia's iron hand in Ukraine's confrontation.
The sudden arrival of men in military uniform patrolling key strategic facilities prompted Ukraine to accuse Russia of "military invasion and occupation" - a claim that brought an alarming new dimension to the crisis.
Oleksandr Turchynov, who stepped in as president after Viktor Yanukovych fled Kiev last weekend, urged Russian President Vladimir Putin to stop "provocations" in Crimea and pull back military forces from the peninsula. Turchynov said the Ukrainian military would fulfill its duty but would not be drawn into provocations.
Associated Press journalists in Crimea spotted a convoy of nine Russian armored personnel carriers on a road between the port city of Sevastopol, where Russia has a naval base, and the regional capital, Simferopol. The tensions at two Crimea airports apparently caused the closure of airspace over the peninsula.
Russia kept silent on claims of military intervention, even as it maintained its hard-line stance on protecting ethnic Russians in Crimea, a territory that has played a symbolic role in its national identity.