A freight train was derailed and a fuel storage tank burst into flames in Russia overnight in an incident Russian media has blamed on a Ukrainian "drone attack".

Flames and plumes of smoke were seen shooting into the night sky, with dramatic images from the scene showing both the moment of the fire and the aftermath of the derailment the morning after.

Russian state news agency Tass said, citing emergency services, said that 300 metres of track had been damaged in the alleged attack, while open-source intelligence figures said nine carriages had been derailed.

Speculation circulated on Ukrainian social media channels about whether the blaze had broken out thanks to a Ukrainian UAV (unmanned aerial vehicle) strike, but this has not been confirmed.

By Tuesday morning, Ukrainian officials had not commented on the incident.

But just two days prior, another fire broke out at an oil refinery in the wider Volgograd region, according to its governor Andrey Bocharov, who blamed the inferno on an overnight drone attack launched from Ukraine.

A Russian Railways statement said: "As a result of interference by unauthorised persons into the operation of railway transport, cars of a freight train derailed at the Kotluban station.

"According to preliminary information, there were no injuries. At this time, train traffic in the area of the Kotluban station is suspended."

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Further footage posted on Telegram showed a large-scale emergency response in the area as cleanup teams scrambled to clear the tracks and repair overhead power lines.

Russia's RIA state news agency reported that the fuel storage tank as well as train cars carrying lumber caught fire before the blaze was extinguished, citing the country's emergency ministry.

Though it is not clear whether the attack or "unauthorised persons" were related to Russia's ongoing war in Ukraine, the latter has previously claimed responsibility for a number of sabotage attacks on Russia's railway system in order to disrupt military logistics.

Ukraine has said that targeting Russia's military, transport and energy infrastructure undermines Moscow's war effort and is an answer to countless attacks on Ukrainian infrastructure by Russia.

Volgograd sits just under 300 miles from the war's front lines in eastern Ukraine - and if Russian state media reports are correct in saying the incident was caused by a Ukrainian attack, it marks just the latest in a string of counter-offensive attacks on Russian soil by Volodymyr Zelensky's forces.

And Zelensky will be buoyed today by the arrival of US Secretary of State Antony Blinken in capital Kyiv, where the pair discussed impending American military assistance packages.

Blinken said: "In the near term, the assistance is now on the way, some of it has already arrived and more of it will be arriving... and that's going to make a real difference against the ongoing Russian aggression on the battlefield."

Zelensky lauded the "crucial" aid package, and thanked Washington for its bipartisan support after Congress voted through the assistance after months of delays.

He said Ukraine's biggest deficit for now was in air defence, telling Blinken that Kyiv needs two Patriot air defence batteries for the northeastern region of Kharkiv, being pummelled by Russian air strikes.

"Civilians, warriors, everybody - they are under Russian missiles," Zelensky added.