Belarus has several battalions equipped with Russian-made S-300 air defense systems on combat duty as part of the Russian-Belarusian integrated air defense network.
"We have completed the first stage of modernization of the Belarusian S-300 air defense systems and agreed to intensify work on further deliveries of these systems to Belarus," Serdyukov said after a meeting of Russian and Belarusian defense officials in Minsk.
Moscow and Minsk signed an agreement in February 2009 on the joint protection of the Russia-Belarus Union State's airspace and the creation of an integrated regional air defense network.
"We are strengthening this network," Serdyukov said.
Modernized versions of S-300 have a maximum engagement range of up to 150 kilometers (93 miles).