MOSCOW (Reuters) - The Russian defense ministry said it had sent Su-27 fighter planes on Wednesday to intercept a U.S. aircraft approaching its border over the Black Sea because the American planes had turned off their transponders, which are needed for identification.

"After the Russian fighters approached the reconnaissance aircraft for visual inspection and identification of the aircraft registration numbers, the American planes abruptly changed course and flew in the opposite direction from the Russian border," a Russian Defense Ministry spokesman, Major-General Igor Konashenkov, said in a statement.

Konashenkov said that the Russian pilots acted in a strict accordance with international rules.

(Reporting by Lidia Kelly; Editing by Louise Ireland)