U.S. believes Russian aircraft shot down by Syria defenses -source

WASHINGTON, Sept 17 (Reuters) - The United States believes that a Russian military aircraft that Russian state media reported "disappeared" on Monday over the Mediterranean was inadvertently shot down by Syrian government anti-aircraft artillery, a U.S. official said.

The official, who spoke to Reuters on condition of anonymity, said the U.S. government's operating theory was that the Syrian defenses accidentally shot down the Russian aircraft while firing at incoming Israeli missiles. (Reporting by Phil Stewart Editing by Yara Bayoumy, Toni Reinhold)