A Kremlin spokesman said on Wednesday he could not rule out that there were Russian civilians in Syria, but that they had no connection to the Russian armed forces.

Associates of Russian military contractors fighting alongside government forces in Syria have said there were large-scale casualties among the contractors when U.S.-led coalition forces clashed with pro-government forces in Syria's Deir al-Zor province on Feb. 7.

Kremlin spokesman Dmitry Peskov, speaking on a conference call with reporters, said he had no information about any such casualties.

Officially, private military companies are illegal in Russia. Putin himself voiced support for them before, in April 2012, Putin suggested the need for “an instrument in the pursuit of national interests without the direct participation of the state,” continuing, “I believe that it should be considered, thought over.”

The St. Petersburg-based website Fontanka reported that about 3,000 Russians under contract to the Wagner group have fought in Syria since 2015, months before Russias two-year military campaign helped to turn the tide of the civil war in favor of Syrian President Bashar Assad, a longtime Moscow ally.

When Putin went to a Russian air base in Syria on Monday and told Russian troops that you are coming back home with victory, he did not mention the private contractors. Russian troops are expected to remain in Syria for years while the contractors are likely to stay to guard lucrative oil and gas fields under a contract between the Syrian government and another Russian company allegedly linked to a businessman known as Putins chef for his close ties to the Kremlin.

Russia has used such proxies before — in the conflict to help pro-Moscow separatists in eastern Ukraine since 2014. One Russian commander boasted of working alongside Russian troops who said they were on vacation while fighting in Ukraine.

As of December 2017, the Defense Ministry has refused to say how many of its troops are in Syria, although one estimate based on absentee ballots cast in the Russian parliamentary election last year indicated 4,300 personnel were deployed there. That number probably rose this year because Moscow sent Russian military police to patrol de-escalation zones.

The Russian people are not very enthused by the idea of an empire that would involve their boys coming home in body bags. Theres clearly a lack enthusiasm for this conflict, said Mark Galeotti, senior researcher at the Institute of International Relations in Prague.

The Russian parliament is working on a bill to regulate private military companies, a senior lawmaker said Wednesday after reports that an unknown number of Russian military contractors were killed in a U.S. strike in Syria.

Retired Gen. Vladimir Shamanov, head of the defense committee in the lower house of Russia’s parliament, said the government needs to oversee private military contractors.

“The state must be directly involved in issues related to the life and health of our citizens,” he said in remarks carried by Russian news agencies.

The Associated Press contributed to this report