Two Russian military planes delivered troops and equipment to Venezuela over the weekend, Russian state news agency Sputnik reported Sunday.
"Two Russian planes arrived in Venezuela on Saturday with equipment and personnel to fulfill technical military contracts," the agency reported on the Spanish-language version of its website.
It gave no other details but quoted an unnamed official from the Russian embassy in Caracas saying "there is nothing mysterious" about the flights.
The Sputnik report was published after an independent Venezuela journalist, Javier Mayorca, said on his Twitter feed that a Russian air force Antonov-124 cargo plane and a smaller jet, apparently an Ilyushin Il-62, had landed at the main airport outside Caracas on Saturday.
He said the planes offloaded around 100 Russian soldiers led by General Vasily Tonkoshkurov, head of the Mobilization Directorate of Russia's armed forces, and disembarked 35 tons of equipment.
Social media and non-state Venezuelan media picked up the information and posted pictures of the planes at the airport.
One picture of a Russian-flagged aircraft posted on social media showed men in uniform clustered around it.
An AFP journalist early on Sunday saw one of the planes on the tarmac at Maiquetia airport, with a Russian flag on its fuselage. It was guarded by a contingent of Venezuelan National Guardsmen.
A picture of a Russian-flagged aircraft posted on social media showed men in uniform clustered around it on the tarmac.
Venezuelan authorities offered no information about the flights. The Russian embassy in Caracas declined to comment to AFP on the reports.
- US tensions -
Russia and China are the main allies of Venezuela. Both have lent billions of dollars to the oil-rich South American country, propping up the anti-US government of President Nicolas Maduro.
Russia has also vocally opposed US moves to sanction Maduro and his government, and to recognize opposition leader Juan Guaido as Venezuela's interim president.
US moves against Caracas have ratcheted up in recent weeks, with President Donald Trump warning that "all options" -- implicitly including US military intervention -- were being considered.
On April 28, US sanctions are to jump up a level with a ban on crude imports from Venezuela. Historically, the US has been Venezuela's biggest oil buyer, and the new sanctions are expected to severely crimp the Maduro government's already badly diminished finances.
Russia previously signaled its support for Maduro by sending two Tu-160 bombers to Venezuela last December to take part in a military exercise.
Russia's President Vladimir Putin has a record of ordering his military -- or paramilitary -- forces into several theaters to challenge US strategies, notably in Syria and Ukraine.
Any Russian foothold in Latin America, especially Venezuela, would alarm the US military. It would also be a political test for Trump, who has routinely avoided criticizing Putin.