WASHINGTON (AP) — The Obama administration expressed growing concern Friday over Russian intentions in Ukraine, with Secretary of State John Kerry delivering a blunt warning to Moscow against military moves in the country’s southern Crimea region that could further inflame tensions.

As pro-Russia gunmen patrolled Crimean streets in armored vehicles and took over airports there, Kerry said he called Russian Foreign Minister Sergey Lavrov for the second time in two days to press the Kremlin to hold to its promise to respect the former Soviet republic’s sovereignty and territorial integrity.