Russia's Voronezh-DM radar site in the southern town of Armavir went into service on Thursday.
Maj. Gen. Oleg Ostapenko said the Armavir radar would monitor missile routes and probable directions for a missile attack in the south and southeast of Russia in place of the early warning facilities in Mukachevo in western Ukraine and Sevastopol, the Crimea.
Russia terminated a 1997 agreement with Ukraine on the use of both Ukrainian radars in February 2008 on the grounds that they had become obsolete.
With an effective range of 4,000 kilometers (2,500 miles) the Voronezh-class radar has capabilities similar to its predecessors, the Dnepr and Daryal, which are currently deployed outside Russia, but uses less energy and is more environmentally friendly.
Gen. Ostapenko said Russia would build more radar stations to replace the existing ones, adding that the Armavir facility was the second, after the Lekhtusi complex, in the Leningrad Region, which had been put into operation in March 2006.
Washington wants to place 10 missile interceptors in Poland and a radar station in the neighboring Czech Republic, purportedly to counter a missile threat from Iran and other "rogue" states. Russia has fiercely opposed the plans, saying the European shield would destroy the strategic balance of forces and threaten Russia's national interests.