A Russian MP who fled Moscow fearing for his life at the hands of President Putin's secret service was assassinated today in the Ukrainian capital Kiev.

Denis Voronenkov, who had testified against the pro-Russian former Ukrainian President, Viktor Yanukovych, was shot dead in broad daylight by an assassin with a 9mm handgun.

His bodyguard was injured but fired back, fatally wounding the gunman, who died a few hours later.

The 45-year-old fled Moscow in October with his wife Maria Maksakova, an opera singer, saying they were fed up of the 'schizophrenic' Russian government.

Maksakova, who had a son with Voronenkov last year, rushed to the scene of the shooting outside a luxury hotel today and broke down in tears.

Ukraine's President Petro Poroshenko said it was an 'act of state terrorism' by Russia and added: 'It clearly shows the handwriting of Russian special services shown repeatedly in various European capitals in the past.'

But Kremlin spokesman Dmitry Peskov said: 'We believe that all the falsehoods that can already be heard about much-hyped Russian involvement are absurd.'

Investigators stand over the body of Denis Voronenkov, a former MP in the Russian State Duma, who was shot dead in Kiev today in an apparent contract killing

Voronenkov is pictured with his wife Maria when she was heavily pregnant. Their son, born in Moscow in the spring of last year, will be a year old next month

Maria Maksakova, wife of Denis Voronenkov, is pictured arriving at the murder scene a few hours after the former Russian MP was gunned down in Kiev

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The bodyguard, who was a member of the Ukrainian security services, remains in hospital.

The Ukrainian authorities said the assassin had been identified as a Ukrainian citizen, although he may be an ethnic Russian from the breakaway east of the country or from the Crimea.

He was shot three or four times and died from wounds to his chest and head.

Writing on Twitter, Ilya Ponomarev, another former Russian MP and critic of Putin who has been in exile since 2014, said Voronenkov had been killed while on his way to meet him.

Ponomarev, who was the only MP in the Russian Duma to vote against the annexation of the Crimea, tweeted: 'There are no words.'

Nikolai Kovalyov, a former Russian security chief who is now an MP, told Russian state television the killing could have been rooted in a business dispute.

Ukrainian Prosecutor-General Yuriy Lutsenko blamed the Kremlin for Voronenkov's killing, saying Russia wanted to punish him for his testimony to Ukrainian investigators.

He said it was a 'cynical murder' of a man who had provided investigators with important testimony about Russian aggression and added: 'This was a typical show execution of a witness by the Kremlin.'

The killing came a few hours after Russian or separatist saboteurs blew up a warehouse storing tank ammunition at a military base in the east of the country.

In Voronenkov's last interview, with Radio Free Europe last month, he said he opposed 'Russia's war' against Ukraine but said it would only end when Putin left the scene.

He also threatened to testify about the involvement of former President Yanukovych - an ally of Putin - in the separatist uprising in eastern Ukraine and said: 'I will talk about criminal deeds of the former president, which led to the ongoing bloodshed in Donetsk and Luhansk regions.'

At the end of the interview with Kiev-based journalist Christopher Miller Voronenkov and his wife laughed as they showed him social media messages calling them 'traitors'.

Miller wrote: 'Maksakova...says of all the attention they have gotten in the past 48 hours: "God, it's so funny!"'

Miller tweeted today: 'As Ukraine's president and prosecutor general jump to cast Voronenkov murder as Kremlin plot, Kiev police tell me still too early to call.'

He added: 'Yes, Voronenkov was viewed in Moscow as traitor - no worse crime. But had enemies in Ukraine unhappy he was welcomed here, given citizenship.'

Voronenkov was wanted in Moscow on fraud charges and Russian media had reported in recent months that he owned five expensive Russian apartments and a fleet of luxury cars.

His name also surfaced in the Panama Papers leak as a shareholder of a company based in the British Virgin Islands.

Voronenkov's bodyguard was injured but managed to shoot back, fatally wounding the assassin (pictured), who died of his injuries in hospital this afternoon

Denis Vorodenkov (pictured left, with his wife Maria Maksakova) was considered a turncoat after he switched from supporting Putin to opposing him and fleeing to the Ukraine

Voronenkov's wife, Maria Maksakova broke down at the scene (pictured left) and had to be escorted away by friends and a bodyguard (right)

Denis Voronenkov (right), who was killed today, fled Moscow, saying he feared President Putin (left) had put out a contract on his life

He said he feared Russia's Federal Security Service (FSB), which took over from the KGB in the 1990s.

Last month, in an interview with Radio Free Europe, Voronenkov compared Putin's Russia with Nazi Germany and said the annexation of the Crimea in 2014 was 'illegal' and a 'mistake'.

In that interview he said he was not interested in Ukrainian politics and only wanted to raise the couple's son, whose first birthday will be next month.

Voronenkov's body is removed from the crime scene by the Ukrainian security forces

Voronenkov's distraught wife Maria rushed to the scene. Last month, in an interview, she laughed off threats from Russians who accused her and husband of being 'traitors'

Russia and the Ukraine have been virtually at war with each other since President Yanukovych was ousted by Ukrainian nationalist demonstrators in February 2014.

Ethnic Russian separatists have set up a rebel republic in the Donbass region of eastern Ukraine and Russia annexed the Crimea, which is dominated by ethnic Russians, in the summer of 2014.

Yesterday the Ukraine forbid Russia's entry to the Eurovision Song Contest, Yulia Samoylova, from taking part in the competition in May because she had toured in the 'occupied' Crimea.

Detectives take photographs of the body of Denis Voronenkov, a critic of President Putin, who was gunned down by an assassin in the Ukrainian capital today

Voronenkov's assassination in broad daylight in a busy Kiev street has been described by the Ukrainians as being a 'show execution'

Voronenkov joins a growing list of critics of Vladimir Putin who have met a bloody end

Ukrainian Prosecutor-General Yuriy Lutsenko today blamed the Kremlin for Voronenkov's killing, saying Russia wanted to punish him for his testimony to Ukrainian investigators.

Voronenkov, who was a former member of the communist faction in the lower house of Russia's parliament, had renounced his Russian citizenship and been granted a Ukrainian passport.

Ukrainian MP Volodymyr Ariev‏ tweeted: 'New Litvinenko case. Former Russian MP Voronenkov shot to death in Kiev right on the street. Putin spreading fear over the world.'

Kiev police chief Andriy Kryshchenko said Voronenkov was killed around noon local time and his bodyguard was injured.

Maksakova, who was also a member of parliament, was not with him at the time but rushed to the scene.

Ukrainian journalists hover around the body as plain clothes detectives carry out a forensic examination of the scene

He was elected in 2011 and was at one point a strong supporter of Putin, having co-authored a 2014 bill which banned the foreign ownership of Russian media, a move described by Bloomberg columnist Leonid Bershidsky as 'perhaps the single worst thing that happened to press freedom as an institution in Putin's Russia'.

But he later changed his position and defected to the Ukraine and since coming to Kiev he had testified against Ukraine's ex-President Yanukovych, who was blamed for the violent crushing of demonstrations by anti-Russian protesters in Kiev's Maidan Square in February 2014.

Svetlana Petrenko, a spokesman for the Russian Investigative Committee, which had been probing fraud allegations against Voronenkov, said: 'In the event of official confirmation of his death, the law provides termination of the criminal case on non-exculpatory grounds with the consent of the relatives of the deceased, or referral of the criminal case to the court for consideration on the merits.'

Voronenkov (pictured, left) was killed in a hail of 9mm bullets, casings of which were found in the street (right)

After he fled to Ukraine, Russian investigators filed fraud charges against Voronenkov in connection with his business activities.

Putin supporters were quick to reject Ukrainian allegations that Voronenkov could have been killed for betraying Russia.

Enrico Ivanov tweeted: 'Voronenkov celebrated Crimea's reunification and criticised regime, he changed point of view in 2016 after he was accused of fraud.'

Ivanov tweeted that Putin critic Alexei Navalny called Voronenkov 'a pig and a thief till 2016 because he was incredibly corrupt. For one time he was right.'

But Anton Geraschenko, an adviser to the head of the Ministry for Internal Affairs of Ukraine, said: 'This is a contractual political assassination, the goal of which is to intimidate all those Russian deputies and officials who will try to escape from Russia to the West or to Ukraine. I offer my sincere condolences to his wife, relatives and friends.'