* Russia and former Soviet republics hold exercises
* First war games by rapid reaction force
* Uzbek and Belarussian leaders absent
(Recasts and adds Medvedev comments)
By Oleg Shchedrov
MATYBULAK, Kazakhstan, Oct 16 (Reuters) - Russia and four former Soviet republics staged war games on Friday to showcase a a new NATO-style rapid reaction force designed to cement Moscow’s hold over allies in Central Asia and the Caucasus.
Dressed in combat fatigues, the leaders of Russia, Armenia, Kazakhstan, Kyrgyzstan and Tajikistan looked on as the force carried out a mock attack to destroy "insurgents" who had taken control of a chemical plant.
Smoke rose from a dew-drenched firing range in the Kazakh steppe, revealing paratroopers landing from helicopters and storming a building to rescue hostages.
Russian President Dmitry Medvedev arrived at the Soviet-era firing range in a helicopter and wore desert-style camouflage uniforms created by fashion designer Valentin Yudashkin.
Russia is building up the Collective Security Treaty Organisation (CSTO), a military alliance among former Soviet republics, as a counterweight to NATO. The organisation commits members to defend each other if attacked.
"This is our answer to those threats which our states are coming up against, threats which know no borders -- drug crime, religious radicalism and several other threats which we all intend to battle," Medvedev told reporters.
"This is a milestone in the development of the CSTO and our cooperation."
Five of the CSTO members agreed to create the rapid reaction force in February, when Medvedev said the units should be comparable to NATO structures.
Officials said 7,000 troops and 90 aircraft took part in the "Interaction-2009" drills, which covered an area of 1,600 square kilometres (600 square miles) at the Matybulak firing range in southern Kazakhstan.
After inspecting troops and weapons, Medvedev and the other leaders moved to a two-storey brick command centre where they watched the exercises for 90 minutes through binoculars.
"We created this organisation to repel aggression on any member of this organisation, to (fight) extremists, terrorists, drug trafficking and other kinds of extremism," Kazakh President Nursultan Nazarbayev told reporters after the manoeuvres.
Belarussian President Alexander Lukashenko and Uzbek President Islam Karimov were absent. Although their countries are members of the CSTO, they have declined to join the rapid reaction force.
Lukashenko’s ties with Moscow have soured over trade rows and anger at Russia’s refusal to lend Belarus more money. Karimov has been irked by Russian plans to build a military base in Kyrgyzstan near Uzbekistan’s eastern border. (Writing by Guy Faulconbridge; editing by Andrew Roche)