UNITED NATIONS (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.
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.
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.
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.