UPDATE: 5:15 a.m. EDT — Russia defended its interception of the U.S. Air Force RC-135 plane over the Baltic Sea, saying it sent its Su-27 fighter jet so close because the American plane had turned off its transponder, which is needed for identification.

"All flights of Russian planes are conducted in accordance with international regulations on the use of airspace," the Russian Defense Ministry said in a statement reported by Reuters. "The U.S. Air Force has two solutions: either not to fly near our borders or to turn the transponder on for identification."

Original story:

A Russian Su-27 jet intercepted a U.S. Air Force RC-135 aircraft which was flying a reconnaissance mission in international airspace above the Baltic Sea, the Defense Department said Friday, according to CNN. The Pentagon said the interception was made in an "unsafe and unprofessional manner."

"The SU-27 intercepted the U.S. aircraft flying a routine route at high rate of speed from the side then proceeded to perform an aggressive maneuver that posed a threat to the safety of the U.S. aircrew in the RC-135," Lt. Col. Michelle L. Baldanza, a U.S. Army spokesperson, said in a statement to CNN.

The Russian jet came as close as about 100 feet of the American aircraft while performing a "barrel-roll," the latest in a series of similar incidents between the U.S. and Russian armed forces.

"This unsafe and unprofessional air intercept has the potential to cause serious harm and injury to all aircrews involved," Pentagon spokesman Commander Bill Urban said in the statement. "More importantly, the unsafe and unprofessional actions of a single pilot have the potential to unnecessarily escalate tensions between countries."

Earlier this month, a Russian Su-24 military jet came within 30 feet of U.S. naval destroyer, the USS Donald Cook, in international waters in the Baltic Sea, raising deep concerns over the Russian flight maneuvers.

"There have been repeated incidents over the last year where Russian military aircraft have come close enough to other air and sea traffic to raise serious safety concerns, and we are very concerned with any such behavior," Urban reportedly said.