MOSCOW (Reuters) - Thousands of Russians have been fighting in Syria in anti-government ranks, Russian Prime Minister Dmitry Medvedev said in an interview published on Saturday, issuing a warning of possible attacks by them on their return home.

Slideshow ( 4 images )

Last year, Moscow launched an air campaign to hit the targets of militants who have waged a war against Syrian President Bashar al-Assad. There are also numerous jihadists from Russia who filled the ranks of anti-government forces.

“You probably know that thousands of Russian citizens and individuals from other post-Soviet republics are fighting in Syria,” Medvedev told Channel 2 Israel ahead of a visit to Israel next week, according to the interview transcript.

“These completely brainwashed people return home as professional murderers and terrorists. And we don’t want them to stage something similar in Russia after their Syrian stints expire.”

“We have already experienced this, including in the context of the Caucasus war in the 1990s. First of all, we want them to stay there. Second, the Syrian Government asked Russian leaders to help them reinstate law and order,” Medvedev said about the wars Moscow waged in Chechnya.

By December 2015, some 2,900 Russians had left to fight in the Middle East, Alexander Bortnikov, director of the FSB, the Russian security service, said at a sitting of the National Anti-terrorist Committee late last year.

According to official data, more than 90 percent of them left Russia after mid-2013.

Moscow is now fighting Islamic State and other militant groups in Syria that the Kremlin says pose a threat to the security of Russia and the world. The Kremlin has justified its campaign of air strikes in Syria by saying its main objective was to crush Islamic State.

Medvedev reiterated that Syrian people should decide their political future and system of the country themselves.

“We don’t know whether this system would have any place for Bashar al-Assad or someone else, this is not our business, and it must be decided by the people of Syria. But we don’t want Syria to disintegrate into a number of enclaves and sectors (in line with a Libyan-style scenario), where each sector would be controlled by separate terrorist groups,” Medvedev said.