WASHINGTON (AFP) - Russia has sent "several hundred" troops into Ukraine's Crimea region, US defense officials said on Friday, after Kiev called on Moscow to withdraw its forces from the peninsula.
The comments marked the first confirmation from President Barack Obama's administration that Russia had launched an incursion into Crimea.
"It looks like they've moved several hundred troops there (into Crimea)," a senior defense official, who spoke on condition of anonymity, told AFP.
The Russians had not given the US government advance notice of the action or explained its intentions since the operation was launched, officials said.
But Pentagon officials stressed Washington was focused on diplomacy, and there was no serious consideration being given to any US military action.
"It is now in the realm of diplomacy," said a second defense official, who asked not to be named.
Officials also said they were not aware of any request from Ukraine for military assistance.
Military officers said so far there were no reports of any armed clash between Russian and Ukrainian troops.
Pentagon spokesman Rear Admiral John Kirby declined to say if the Obama administration shared Ukraine's view that the Russians had staged an "invasion" of Crimea.
"We're assessing the situation, and we are not prepared to characterize it," Kirby told reporters.
US officials pointed out that Washington did not intervene in a conflict in 2008 when Russia sent troops into Georgia over the disputed breakaway provinces of South Ossetia and Abkhazia.
Ukraine's interim president Oleksandr Turchynov earlier accused Russian soldiers and local pro-Kremlin militia of staging raids on Crimea's main airport and another base on the southwest of the peninsula where pro-Moscow sentiments run high.
AFP reporters in Crimea said dozens of men in battle fatigues and armed with Kalashnikovs encircled Simferopol airport late on Friday.
Witnesses also reported seeing several armored vehicles rumble across Simferopol's main streets and at least eight cargo planes bearing the Russian tricolour flag landing at a Ukrainian military air base just north of the city on Friday evening.