RNA - CSTO is a military alliance comprising Armenia, Belarus, Kazakhstan, Kyrgyzstan, Russia and Tajikistan, RIA Novosti reported.
"About 2,000-2,500 people, some of them are fighting, some have returned," acting CSTO Secretary General Valery Semerikov said when asked how many Russians were fighting in Syria on the terrorists' side.
Security forces foiled 16 terror attacks in Russia and 35 attacks in Tajikistan in 2016, Semerikov said.
"In 2016 16 terror attacks were foiled in Russia, 35, in Tajikistan," he said presenting the report on terror and extremist threat in Central Asia and Afghanistan.
Semerikov pointed out that 149 terror attacks in 29 countries were committed last year with 43 of them having been staged in Turkey and 55 in Afghanistan.
CSTO member states faced eight terror attacks in 2016, according to Semerikov.
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