Russia is moving nuclear-capable missiles into Kaliningrad, a tiny Russian enclave between Poland and Lithuania, a U.S. intelligence official said Friday, confirming Estonian news reports.

Russia's reasons for shipping the Iskander-M missiles to Kaliningrad "could be innocuous," said the official, who spoke on condition of anonymity.

"They moved a similar missile system to Kaliningrad in 2014 for a military exercise. It could also be a political gesture — a show of strength — to express displeasure with NATO," said the official. The missiles have a range of 500 kilometers (300 miles).