One of Russia's most outspoken independent journalists has died in a mysterious incident on his motorbike - soon after a savage attack on the authorities over Sunday's fatal Sukhoi SuperJet inferno in Moscow.

Sergey Dorenko, 59, editor in chief of Govorit Moskva radio station, was shown in a CCTV video lurching to the left in front of oncoming traffic on a busy city street.

He fell from his new Triumph motorbike but was not hit by another vehicle.

Sergey Dorenko, 59, was seen on CCTV swerving in front of oncoming traffic on a busy Russian street

Dorenko died after falling from his Triumph motorbike on Thursday evening shortly before 7pm

He was pronounced dead at the spot with reports in the official media rapidly stating he had suffered 'major heart failure' and died of 'natural causes' - even before any autopsy was conducted.

Dorenko was known for his laser-like criticisms of the Russian authorities over a succession of disasters in which he believed the causes of deaths were being covered-up.

Most recently he raised awkward questions over Sunday's passenger jet tragedy in Moscow in which 41 perished.

Russian state media reported that Dorenko died of 'natural causes' and crashed his motorbike due to a heart problem

Dorenko often criticized the Russian government - most recently over the passenger jet tragedy in Moscow which killed 41 people on Sunday

Earlier he was fired in 2000 as a top presenter on Russia's main state-run channel after blunt criticism of Vladimir Putin for 'lies' over the Kursk submarine tragedy in which all 118 crew were killed.

The prominent journalist was among the first to reveal on Sunday that there had been fatalities on the blazing SuperJet plane after an emergency landing in Moscow - when initial reports claimed everyone had successfully evacuated the burning aircraft.

Later he blasted the authorities for not grounding the plane in characteristically forthright language.

Sergey Dorenko (pictured) was well-known for his criticisms of President Vladimir Putin's government

The site of a road accident involving Russian journalist Sergei Dorenko. Dorenko died after falling from a Triumph motorcycle

In particular, he attacked an effort to blame the crew for a disaster that many suspect is the fault of technical problems with the Sukhoi plane.

He stated: 'I see a lot of fuss around the burned plane. And I think this fuss is shady. The time has come to sort it out. We need a reasonable evaluation of what happened at Sheremetyevo airport.

'We need sharp facts, solid links between the reasons and consequences, truth about an accident or a systematic mistake. Am I right?

'But so far we see only emotions, hysteria and an attempt to push somebody's head into the toilet bowl.

'For example, it is very strange that a representative of the company Sukhoi Civil Aircraft joined the investigative commission (into the air disaster).

Sergey Dorenko on his new Triumph motorbike, which he was riding at the time of the fatal accident on Thursday

'It means the participation of interested parties in the investigation. It is a ruined investigation from the very beginning.'

He asked the authorities: 'Do you think we are idiots? Stop gambling, damn it. We are talking about the trust in our aviation.

'Sukhoi and Aeroflot - stop covering your arses, you will ruin the system and crash down with it….'

'Let's try to play in an honest way?'

Father-of-five Sergey Dorenko with one of his daughters

He also scathingly attacked Putin's government and regulators for not grounding the SuperJet.

In a succession of angry posts, he asked: 'Do you not care about people? You f*** the people.

He accused the authorities of letting the plane fly when they knew it had problems.

'The plane is very bad, it was known from the very beginning,' he said.

He also backed a call that Russian officials should be made to fly only in SuperJets if they were so confident of its airworthiness.

In 2000, he was famously fired from Channel One television in Russia after directly criticising Putin in blunt comments on the Kursk submarine tragedy when 118 sailors died in the sunk nuclear-powered vessel.

He told viewers: 'The story with the Kursk submarine is not over. The main conclusion is that (those in) power do not respect us… this is why they lie.

'And the main thing – power treats us in such a way only because we allow it to do so.'

Suspecting he would be axed, he finished his report: 'All the best to you.'

Last year Dorenko was blunt in his analysis when Russia's prosecutor-general Saak Karapetyan was killed in a mystery helicopter crash.

Dorenko is pictured on holiday with his third wife Yulia, with whom he had two young daughters

The law chief has been linked to Moscow's alleged offers of 'dirt' on Hillary Clinton to Donald Trump's election campaign.

There were also extraordinary claims that he was a channel of leaks to British, US and Swiss secret services.

Dorenko reported: 'We have the official version that the pilot mistakenly touched the trees and the helicopter fell to the ground.

'But in fact I suppose that the pilot was good and did not touch any trees.

'He did not take off at all. He was shot with two bullets in the back before this.'

Dorenko did not work for state TV after his Kursk firing - but became editor-in-chief of the Govorit Moskva radio station.

Sergey Dorenko on his appearance for Russian state TV in 2000, before he was fired for criticizing Putin

Dorenko was known for his laser-like criticisms of the Russian authorities over a succession of disasters

In 2007 when he released an interview that he had conducted in April 1998 with FSB officer Aleksander Litvinenko and other FSB officers in which they confessed that they had been ordered to kill, kidnap, or blackmail prominent politicians and businesspeople.

Litvinenko died in London in 2006 of acute radiation poisoning after his tea was spiked.

A British criminal investigation found he was poisoned with polonium 210 by Andrei Lugovoy, now a Russian MP.

Lugovoy and the Russian government denied any role in the dissident's death.

The Russian state media reported that Dorenko had died of 'natural causes' after falling off his motorbike due to a heart problem.

Yet this was state before any postmortem.

A driver who witnessed Dorenko's accident said he fell off before the motorbike even came to a halt, saying he was unconscious, and did not say a word

A source told Interfax news agency: 'His heart stopped and he could not control his bike anymore.

'The injuries that he got when falling from his motorbike were not serious.'

Yet RIA Novosti reported: 'When somebody dies in the street, paramedics automatically put it as "major heart failure".

'In the case of Dorenko it is a preliminary reason. The true cause will be known only after autopsy. It is not possible to learn the reason for death within one minute.'

A driver who witnessed the accident said: 'I was driving my car at Zemlyanoy Val towards Taganskaya Square. The motorbike was driving towards me.

'Suddenly it skidded, going to the side, hit the fence, but the motorcyclist fell off even before and rolled along the pavement.

'I stopped and helped to drag him to the side of the road.'

Dorenko's wife Yulia and their two daughters. Dorenko also had three children from previous relationships

The witness added that motorcyclist was unconscious, and did not say a word.

'His eyes were open, there were no visible traumas on his body.'

Dorenko was married to Yulia and the couple had two young daughters. He had three older children by two ex-wives.

Moscow Mayor Sergey Sobyanin, a close Putin ally, expressed his condolences to the family.

'Sergey Dorenko has died. A talented journalist, an anxious and not indifferent person,' he said.

'Sergey loved our city. He died just the way he lived – negotiating a narrow curve. To be honest – it is such a pity.'