At least 4,000 Russian nationals and 5,000 citizens of former Soviet republics have fought for militants in Syria, President Vladimir Putin estimated last year. Analysts believe more foreign fighters have streamed into Syria and Iraq from Russia than any other country.

Russia and its neighbors are on a manhunt for 9,000 suspected terrorists, including 5,000 fighters who took direct part in armed conflicts.

“As of September this year, there is an interstate manhunt for more than 9,000 CIS citizens who committed terrorist and extremist crimes,” Andrei Novikov, the head of the Commonwealth of Independent States’ (CIS) Anti-Terrorism Center, said at anti-terror drills in northern Kyrgyzstan on Wednesday.

Around 5,000 of those are mercenaries who took part in hostilities in other countries “as members of illegal armed groups and international terrorist organizations,” he was cited as saying by the state-run TASS news agency.

A total 83 terrorist suspects have been caught with the help of the CIS Anti-Terrorism Center since 2015, in addition to 207 suspects who helped finance terrorists, Novikov told TASS.

The CIS includes oil-rich Russia, Kazakhstan and Azerbaijan as well as Tajikistan, Kyrgyzstan, Uzbekistan, Belarus, Armenia and Moldova.

On Tuesday, Novikov warned that Islamic State fighters were attempting to create sleeper cells across Central Asia.

Armenia is set to hold next year’s joint CIS anti-terrorist exercises, Novikov said. Around 2,000 Russian and Kyrgyz troops took part in this year’s drills, as well as 400 warplanes and weapons systems, including Iskander-M missile launchers.

Islamic State is a terrorist organization banned in Russia.