Russia launched a pair of classified military satellites into Earth orbit Monday aboard a Kosmos-3M rocket.

The Russian booster lifted off at 0636 GMT (2:36 a.m. EDT) from the Plesetsk Cosmodrome in northern Russia.

The secret cargo consisting of two spacecraft -- dubbed Kosmos 2390 and Kosmos 2391 -- were placed into an orbit of approximately 1465 by 1505 km, inclined 82.5 degrees, according to Western space watchers.

Experts aren't exactly sure what the satellites will be used for since their orbit is different than past military craft launched by Kosmos-3M rockets.