Two Spanish fighters were ordered to intercept two Russian Su-24 aircraft, which were flying over the international waters of the Baltic Sea.
Sanchez was forced to interrupt the press conference held at a NATO air base in Lithuania.
When resuming the press conference, Sanchez said: "This incident justifies the presence of Spanish forces in Lithuania."
Andreus Dilda, a spokesman for the Lithuanian Army Staff, said that the two Russian planes took off from the neighboring Russian enclave of Kaliningrad, and their transmitters and receivers were turned off.
He added that the pilots did not provide the flight plan or radio communications with the regional air traffic control center.