As details continue to emerge about multiple Russian fighters killed in U.S. air and artillery strikes in Syria last week, the Kremlin and senior Russian officials are choosing their words carefully.

Russian President Vladimir Putin has yet to publicly address the February 7 air strikes on Syrian government forces near Deir al-Zor that the Pentagon says killed around 100 fighters who attacked a base housing Syrian opposition and U.S. forces.

Russian media reports have confirmed that several of those killed in the strikes were Russian mercenaries, though the Kremlin is publicly emphasizing that any of its citizens who may have been killed in the U.S. operation had no formal connection to Russian military operations.

"Here in the Kremlin we don't have detailed information that would allow us to make any conclusions," Putin's spokesman, Dmitry Peskov, was quoted by Russian news agencies as saying on February 14.

"We can't exclude the possibility that Russian citizens may be present in Syria. They are not connected to the [Russian] armed forces," Peskov said, adding that Russian citizens "remain Russian citizens no matter what."

The Russian Foreign Ministry, meanwhile, attacked what it called "disinformation" about the deaths in Western media reports, which quoted unidentified Russian and Syrian sources as saying that dozens of Russian mercenaries may have been killed in the incident.

"Reports disseminated by several Western media outlets about hundreds, dozens of dead in Syria is classic disinformation," Russian state news outlets quoted an unidentified ministry official as telling journalists on February 14.

The official, however, did not deny that Russian fighters were killed in the air strikes, according to the agencies' reports.

Moscow and Washington are backing different sides in the war in Syria. Russia has propped up its ally, Syrian President Bashar al-Assad, while the United States and its allies are supporting rebel groups seeking Assad's ouster.

Donbas To Damascus

The incident has brought renewed focus on the role of Russian soldiers of fortune in the conflicts in Syria and Ukraine.

Several of the Russian fighters reportedly killed in the air strikes had previously fought against Kyiv's forces in eastern Ukraine, according to interviews with their relatives and associates in the Russian media this week.

Russia denies backing armed separatists in eastern Ukraine despite substantial evidence of such support in a conflict that has killed more than 10,300 since April 2014.

In an interview with the Russian news site Znak.com this week, the wife of one of the Russians reportedly killed in the air strikes said that his former fellow fighters in eastern Ukraine, an area commonly referred to as the Donbas, had informed her that her husband had died.

Yelena Matveyeva said in the interview that her husband, Stanislav Matveyev, had coordinated with a St. Petersburg firm known as PWC Vagner, a prominent private military company whose fighters have served alongside the Russian military.

Zakhar Prilepin, a Russian writer who fought against Kyiv's forces in eastern Ukraine, said in a February 14 Facebook post that another Russian reportedly killed in the U.S. air strikes -- Igor Kosoturov -- had served in his battalion in the conflict.

Prilepin described Kosoturov as a former Russian military intelligence captain who had retired by the time he fought in eastern Ukraine and Syria.

'Mountain Out Of A Molehill'

Russian lawmakers who frequently rail against Washington have been largely silent on the reported deaths of the Russian mercenaries.

Vladimir Shamanov, the head of the Defense Committee in the lower house of parliament, has previously called the U.S. presence in Syria "arrogance of the highest degree."

But he refrained from attacking Washington on February 14, saying there was not enough "verifiable information yet" about the U.S. air strikes and the deaths of Russian mercenaries. "There are many signs that someone is intentionally trying to make a mountain out of a molehill," the Interfax news agency quoted him as saying.

Another lawmaker in the lower house of parliament, Mikhail Yemelyanov, said on February 14 that draft legislation on regulating private military firms was being examined in parliament.

Writing for Bloomberg View, Leonid Bershidsky said Putin could face mounting pressure from nationalist corners of Russia's political landscape over the deaths of Russian fighters at the hands of the United States amid the ongoing tensions between the former Cold War foes over the conflicts in Ukraine and Syria.

"They will...draw attention to Putin's inability to respond to carnage unleashed on Russian citizens by the U.S. -- the country now seen in Russia as its biggest enemy," Bershidsky wrote in a February 14 column.

The incident has also injected an unexpected sliver of drama into the Russian presidential campaign ahead of a March 18 election in which Putin is expected to easily secure a new six-year term.

Liberal candidate Grigory Yavlinsky said in a February 12 statement that the Russian leadership's taciturn response to reports of the Russian deaths in Syria last week was "absolutely unacceptable."

"Statements about the noninvolvement in the government with the actions of private military structures is reminiscent of how the government washed its hands of the deaths of Russian soldiers sent into wars in Chechnya" and eastern Ukraine, Yavlinsky said.

Peskov on February 13 pushed back against that call by Yavlinsky, an opponent of Russian military involvement in Syria and Ukraine whose candidacy is seen as posing little threat to Putin's reelection. "We are operating on information published in the media. I don't think that Mr. Yavlinsky has sources that are any more reliable. But in this particular case, we nonetheless ask that media reports not be used as a primary source," Peskov said.

"Let's all be realistic about the fact that there are quite a few of our compatriots in many countries of the world," he added.

Vladimir Frolov, a well-connected political analyst in Moscow, said on February 14 that the Kremlin's reticence regarding the Russian deaths was less driven by domestic political considerations than the prospects of escalation with Washington. "No one wants to start a war with the U.S.," Frolov told RFE/RL.

The U.S. military has also said that it does not have information about private Russian soldiers killed in the air strikes.

Peskov told reporters in Moscow on February 14 that Putin did not discuss the incident with U.S. President Donald Trump two days earlier, the Interfax news agency reported.