The murder of opposition politician Boris Nemtsov close to the Kremlin makes him the latest vocal critic of Russian President Vladimir Putin to die violently or in suspicious circumstances.
The former deputy prime minister was gunned down in central Moscow while walking home from a restaurant with his girlfriend on Friday.
Mr Putin has pledged a full investigation into his death and said he will take personal charge of it.
Some activists have accused Mr Putin of being responsible, while his supporters have suggested Mr Nemtsov’s murder may have been a provocation aimed at tarnishing the president’s image.
No suspects have been arrested following the murder, considered the one of the most shocking in a long list of suspected political assassinations during Mr Putin’s rule.
The Kremlin has denied any involvement in the deaths of these high-profile activists, politicians, journalists and lawyers.
:: Alexander Litvinenko – 2006
Former Russian spy Alexander Litvinenko died in November 2006, almost three weeks after drinking tea poisoned with radioactive polonium-210.
It is understood he ingested the tea during a meeting with two fellow former Russian spies, Andrei Lugovoi and Dmitri Kovtun, at the Millennium Hotel in London’s Grosvenor Square. Both deny any involvement in his death and remain in Russia.
Before fleeing Russia and being given British nationality, Litvinenko had accused Mr Putin of corruption. He also blamed Mr Putin for a number of apartment block bombings which helped start the Second Chechen War in 1999, the popularity of which helped bring him to power.
:: Anna Politkovskaya – 2006
The 48-year-old journalist, a prominent critic of Mr Vladimir Putin, was gunned down at her Moscow apartment block on 7 October 2006, the president’s birthday. She was shot twice in the chest, once in the shoulder, and once, at point blank range, in the head
Five men were found guilty of the killing, including the gunman Rustam Makhmudov, although it is not yet known who ordered the killing.
Ms Politkovskaya specialised in uncovering state corruption and rights abuses. She won international acclaim for her reports in the Putin-critical newspaper Novaya Gazeta, about Russian abuses in Chechnya, and for her book Putin’s Russia.
:: Sergei Magnitsky- 2009
Lawyer Sergei Magnitsky died in police custody in November 2009 after allegedly being denied medical treatment and brutally beaten.
He had been instructed by British-American businessman William Browder to investigate a multi-million tax fraud against the Russian state which Mr Browder’s businesses had become unwittingly involved in. But when Magnitsky found evidence suggesting that police officials were behind the fraud, he was arrested and charged with having carried it out himself.
In July 2012 he was convicted – three years after his death – of tax evasion. Mr Browder successfully lobbied the US government to impose sanctions on those linked to Magnitsky’s death.
:: Natalia Estemirova – 2009
The prominent human rights activist was found dead hours after being kidnapped on 15 July, 2009, in the Chechen capital, Grozny.
The 51-year-old had collected evidence of human rights abuses in Chechnya since the start of the second war there in 1999.
She also worked with the investigative journalist Anna Politkovskaya, who was murdered in 2006.
:: Stanislav Markelov and Anastasia Baburova – 2009
Leading human rights lawyer Stanislav Markelov was gunned down in broad daylight on 19 January, 2009.
Journalist Anastasia Baburova, 25, was shot dead after she tried to come to his assistance.
Mr Markelov had just held a press conference to protest at the early release of an army colonel who was jailed for the killing of a young Chechen girl. He had also represented the murdered journalist Anna Politkovskaya.
:: Paul Klebnikov – 2004
Another investigative journalist, Paul Klebnikov, an American of Russian descent, was killed outside his office in a drive-by shooting in Moscow in 2004. He was the editor of Forbes Russia.
Mr Klebnikov had written about corruption in Russia and Forbes had published a list of Russia’s richest people.
:: Sergei Yushenkov – 2003
The co-chairman of the Liberal Russia movement was murdered outside his home in Moscow, on 17 April 2003.
According to the Moscow Times, he was gunned down just hours after the Justice Ministry officially registered his Liberal Russia movement as a party.
:: Boris Berezovsky – 2013
Once one of the most powerful men in Russia, the self-made tycoon was leader of the so-called “oligarchs” who wielded power during the presidency of Boris Yeltsin in the 1990s.
But after falling out with Mr Putin – who is said to have been handpicked by Berezovsky as Yeltsin’s successor – he fled and settled in Britain, where he became an outspoken critic of the new president.
He was found dead at his Berkshire home in March 2013 in an apparent suicide, although an inquest into his death recorded an open verdict.
SUSPECTED SHOW TRIALS
Alongside the suspicious deaths, there have been a series of criminal cases condemned as political “show trials” by critics of Mr Putin. Most recently was the case of anti-corruption blogger Alexei Navalny.
The Kremlin denies any political motivation and insists the judiciary is independent.
:: Alexei Navalny
The 38-year-old lawyer and activist rose to prominence by exposing political corruption in his blog before becoming a prominent speaker at anti-Putin rallies. He coined the phrase “party of crooks and thieves” to describe United Russia, Mr Putin’s party.
He and his brother Oleg were charged with defrauding several companies, including the Russian subsidiary of the French cosmetics company Yves Rocher.
He was convicted in December of fraud and given a three-and-a-half-year suspended sentence. His brother Oleg was jailed for the same period.
:: Sergei Udaltsov
The leader of the Left Front political grouping, the 37-year-old has described himself as a “Soviet patriot”. He and his wife Anastasia have been nicknamed “Russia’s Revolutionary Couple”.
After playing a prominent role in anti-Putin protests, Mr Udaltsov was charged over a demonstration held the day before Mr Putin’s inauguration for his third term as president in May 2012.
He was jailed for four and a half years for organising the protest, which had turned violent.
:: Leonid Razvozzhaev
A Left Front colleague of Sergei Udaltsov, he faced the same charges but fled Russia and tried to seek political asylum in neighbouring Ukraine.
He claimed that while his application was being considered, he was kidnapped, taken back to Russia, tortured and forced to sign confessions which he subsequently disowned.
Russian authorities insisted that he had given himself up voluntarily.
He was sentenced to four-and-a-half years in prison.
:: Mikhail Kosenko
The political activist was convicted of using violence against police officers during the same Bolotnaya Square protests that Sergei Udaltsov and Leonid Razvozzhaev were jailed for organising.
Despite testimony that he was a peaceful demonstrator, Mr Kosenko was sentenced to indefinite psychiatric detention. He was released in July 2014.
Amnesty International said: “Kosenko’s only ‘crime’ was publicly expressing his beliefs. This is reminiscent of the Soviet-era tactics when the authorities used psychiatric treatment to silence dissenting voices.”
In September 2013, 30 Greenpeace activists, including six Britons, were arrested for taking part in a protest at an Arctic oil installation.
They were initially charged with piracy, which could have carried a prison term of up to 15 years. The charge was downgraded to hooliganism, which still could have carried a seven-year term, before they were released after two months in detention.
At the time Mr Putin said their treatment should serve as a lesson to others and suggested unnamed foreign rivals could have been behind their actions.
:: Pussy Riot
The all-female punk group were jailed for two years for hooliganism for performing an anti-Putin song in Moscow’s main cathedral in March 2012.
They were freed in an amnesty initiated by Mr Putin in December 2013 shortly before the Winter Olympics in the Russian city of Sochi.
:: Vladimir Yevtushenkov
One of Russia’s richest men, the billionaire was placed under house arrest in September on suspicion of money-laundering over his purchase of a controlling stake in oil company Bashneft.
He was released from house arrest on 17 December and was praised in Mr Putin’s annual press conference two days later.
However, Kremlin critics say the case is part of a bid by the Russian government to regain control of oil and gas assets sold off in the chaotic privatisations of the 1990s.
The arrest has led to comparisons with the case of Mikhail Khodorkovsky.
:: Mikhail Khodorkovsky
Mr Khodorkovsky was one of the original “oligarchs” – the tycoons who took advantage of the collapse of the Soviet Union in the early 1990s to make their fortunes, before using their clout to effectively rule Russia during the weak presidency of illness-plagued Boris Yeltsin.
In 2003 Mr Khodorkovsky was arrested on charges of fraud. He was jailed for nine years and his oil company Yukos broken up by the state. He and his business partner, Platon Lebedev, were put on trial again in 2010, this time for embezzlement, and were jailed for another four years. Mr Khodorkovsky was suddenly released in December 2013.
Both trials were seen as politically-motivated and a signal from Mr Putin to the rich and powerful to think twice before supporting opposition parties.
Source: Sky News