Flames are pictured rising from the Angarsk facility, which produces jet fuel and diesel which can be used by Russia's military vehicles
The blast struck Angarsk Oil Refinery, near the Siberian city of Irkutsk, around 5.50am local time Thursday - lighting up the early morning sky with a fireball.
Two people were killed and five injured in the explosion, which officials say was caused by 'gas contamination' of the plant's equipment though it is unclear whether this was an accident or whether it was sabotaged.
It comes against the backdrop of multiple blasts and fires at locations with links to Russia's military or oligarchs that many suspect are being orchestrated by Ukraine.
Comment: This is not exactly true, because two of the most recent fires were at shopping malls.
The Angarsk refinery produces jet fuel and diesel that can be used by Russia's military and is owned by oil giant Rosneft, which is owned by Putin ally Igor Sechin.
Comment: Rank Western lie. Rosneft is state-owned. Sechin is CEO. He doesn't "own" the company. The Russian people do. Unlike BP and Shell, which the British people do not own...
It is the second fire in less than a month at the refinery, with an earlier incident reported on 27 November.
Angarsk is located almost 3,000 miles away from the frontlines in Ukraine.
Explosions is the last two weeks rocked Russian energy storage facilities in the Kursk and Bryansk regions, which sit closer to the border with Ukraine.
As happened at Angarsk, the blasts took place in the early-morning hours and focused on energy infrastructure.
Two more explosions hit Russian airbases at Saratov and Ryazan, damaging nuclear-capable bombers being used for attacks on Ukrainian power stations.
Those are thought to have been caused by Ukrainian drones equipped with explosives. The cause of the other blasts in unknown.
Lyubov Volokitina, a Siberian local commenting on today's explosion, said: 'My husband got up, went downstairs, poured himself a coffee and looked out the window to see the Christmas tree in our yard, which we decorated yesterday.
'Suddenly there was an explosion, a glow. I thought that a plane fell on us...
'My daughter [14] cried, frightened, and ran to me from her room. My mother phoned in panic.'
Tatyana Borovaya, from nearby village Meget, said: 'I thought war had started.... It was as if a wave passed through the house, it was shaking.'
Olesya, a local woman posted: 'I live at the end of Novo-Lenino area, and at 6am I woke up from my bed rocking.
'The floor lamp swayed. I live on the 17th floor. I thought it was an earthquake.'
Another local said: 'I was on my way to the bus at 5:55am and saw a bright flash in the sky, then an explosion and a blast.
'The roof of the house I was walking past, cracked from the blast wave. My work colleague said they felt a blast wave in Irkutsk.'
A major Russian oil and gas refinery near the city of Irkutsk, in Siberia, has exploded this morning in the latest case of an early-morning blast at an infrastructure facility
Footage showed the destruction of buildings at the refinery site.
More than 100 people were involved in fighting the flames, it was reported.
Locals questioned whether it was safe to send their children to school, fearing pollution released by the blast.
A student posted: 'Any news for us? Should I go to a college, or find a gas mask?'
Comment: Hmmm... is the re-entry of a long-range rocket visible as a 'bright flash in the sky' moments before impact?
Not to our knowledge.
It could be that eyewitnesses simply saw the explosion first, then heard it as the soundwave reached them afterwards.
But if there really was something streaking through the sky towards the refinery, then what on Earth was it?
The US-EU-Ukraine aren't firing missiles at Siberia, surely?
Below are just some of the most recent suspect fires and explosions in Russia. We suspect that most of them are due to sabotage and/or remotely-activated cyberattacks.