Russian private security contractors have travelled to Venezuela to provide security to the embattled president Nicolás Maduro, the Reuters news agency has reported.

Citing three sources, the news agency said that the mercenaries are linked to the Wagner group, which has carried out missions in Ukraine and Syria and is now reportedly active in countries in Africa, too.

If it is confirmed that contractors from the group traveled to Venezuela, this would be their first known deployment in the western hemisphere.

“The order came down on Monday to form a group to go to Venezuela. They are there to protect those at the highest levels of the government,” Yevgeny Shabaev, a Cossack leader with ties to military contractors, told the Guardian by telephone.

Shabaev, one of the sources cited by Reuters, is a campaigner for the rights of veterans, a group that overlaps heavily with those who join mercenary groups in Russia. He said he had been told about the trip by the relatives of the military contractors. A government spokesman did not immediately respond for comment about the report, although he had earlier told Reuters that the Kremlin had “no such information”.

The report comes after the US threw its support behind opposition leader Juan Guaidó, who declared himself president on Wednesday.

Russia and China, both of which have invested heavily in the country, have attacked the US for encroaching on Venezuela’s sovereignty. The Russian president, Vladimir Putin, on Thursday accused the US of “destructive interference from abroad.” The Russian prime minister, Dmitry Medvedev, called it a “quasi-coup”.

The crisis has produced a familiar standoff, with a US-led coalition on one side and Russia and China on the other. But the distances involved have made the conventional wisdom here that Russia is unlikely to provide direct military support to Maduro’s government to avert a US military intervention.

Russia is an important source of financial support to the Venezuelan government, providing billions of dollars in loans, some as pre-payment for future deliveries of oil. Last month Russia dispatched two nuclear-capable Tu-160 bombers to the country in a further show of support.

While Shabaev said that the deployment of military contractors could be as large as 400 people, other sources cited by Reuters suggested the groups were smaller. There were conflicting reports about when the mercenaries may have arrived as well.

One of Reuters’ two anonymous Russian sources, who the news agency said is close to the Wagner group, said the contractors first arrived in advance of the May 2018 presidential election, but another group arrived “recently”.