MINSK, September 18 (RIA Novosti) - The first phase of joint Russian-Belarusian military exercises began on Friday with the involvement of some 100 aircraft and 12,600 military personnel, the Belarusian Defense Ministry announced.

The five-day first phase of the joint Zapad 2009 (West 2009) anti-aircraft defense exercises will concentrate on the preparation of defense operations of the regional forces. The second phase of the exercises, on September 23-29, will focus on the effectiveness of the unified regional anti-aircraft defense systems of Russia and Belarus.

The exercise will, among other things, rehearse interoperability within the framework of the Belarusian-Russian integrated air defense system, which the two countries agreed to establish in February.

According to the Belarusian Defense Ministry statement, 63 airplanes, 40 helicopters, 470 infantry fighting vehicles, 228 tanks and 234 artillery systems will participate in the exercises. S-300 air defense missile systems will also be used.

S-300s are considered one of the world's most effective all-altitude regional air defense systems, comparable in performance to the U.S. MIM-104 Patriot system.

Belarus has several Russian-made S-300 air defense battalions on combat duty, and has long been negotiating the purchase of advanced S-400 systems from Russia, which should be available in 2010.

Besides the 12,600 Russian and Belarusian military personnel, around 30 Kazakh military personnel will also participate.