(Adds details and context)
MOSCOW, March 28 (Reuters) - Moscow faces growing threats from the United States and its allies, who are trying to weaken Russia's influence on Ukraine, a senior security official was quoted as telling President Vladimir Putin on Friday.
"There has been a sharp increase in external threats to the state. The lawful desire of the peoples of Crimea and eastern Ukrainian regions is causing hysteria in the United States and its allies," Interfax quoted Alexander Malevany, deputy head of the Federal Security Service, as saying.
He said Russia was taking "offensive counter-intelligence and intelligence measures" to blunt Western efforts to "weaken Russian influence in a region that is of vital importance", Interfax reported.
The report indicated Malevany had given no details about the measures, but the remarks could increase Western concerns that Moscow may have designs on eastern Ukraine after annexing the Crimea region, a move that has caused the biggest crisis in East-West relations since the Cold War.
U.S. President Barack Obama said on Friday that a build-up of Russian troops near Ukraine's eastern border may be more than just an effort to intimidate Ukraine, and urged Moscow to pull its forces back to ease tension.
Russia took military control over largely ethnic-Russian Crimea before its citizens voted to join Russia in a March 16 referendum dismissed in the West as illegal.
Putin has received permission from parliament to send the armed forces into Ukraine if necessary, raising concerns that he could cite alleged threats to Russian-speakers in eastern regions as grounds for intervention.
(Writing by Steve Gutterman, Editing by Timothy Heritage and Kevin Liffey)