Vladimir Putin 'has lost all restraint' after murdering Alexei Navalny and will launch a 'killing spree' against his enemies in Britain, with 'at least a dozen names on his hit list'

Vladimir Putin will launch a 'killing spree' against his UK enemies, a Kremlin critic has warned - claiming he has 'lost all restraint' since Alexei Navalny's death.

Activist Bill Browder claimed the Russian president has at least 12 names on his hit list, and is afraid the president will launch attacks on his enemies in Britain.

The multi-millionaire has warned that the Russian president must be stopped to avoid a repeat of the Salisbury Novichok attack.

Speaking to The Mirror, he said Navalny's suspicious death was a 'game changer' for Putin and that critics of the Russian leader are at an increased risk of being assassinated.

The warning comes after Navalny's widow accused Putin of murdering her husband, claiming he was poisoned with the nerve agent Novichok and that Russian authorities are trying to cover up the assassination by refusing to release his body. 

Mr Browder told The Mirror that Putin will 'will embark on a killing spree which will include all enemies in the UK'.

He claims the Russian president has been emboldened following the death of the activist's friend Navalny.

The human rights campaigner, who reportedly became Putin's 'number one enemy' for fighting against corruption, said: 'The fact he would kill the most popular and prominent opposition politician in plain sight without fear of repercussion says that people who are opposing Putin in Russia and abroad are in much more serious risk of assassination.

'The killing of Alexei Navalny has shown Putin has lost all restraint and that he will embark on a major ­international killing spree which will include against all his enemies in the UK.'

Since the murder of Mr Browder's lawyer and whistleblower Sergei Magnitsky in 2009, he has been fighting against Putin's regime.

He called the leader a 'murderous gangster' and demanded he be stopped before he causes 'World War Three'.

Mr Browder is currently fighting to free imprisoned British-Russian ­journalist and political opposition campaigner Vladimir Kara-Murza. 

Serving a 25-year sentence, his friend - who helped promote the Magnitsky Act, named after murdered Sergei - has survived two poisoning attempts, he says. 

It comes after the revelation that Navalny was likely killed by a single punch to the heart, a technique used by the KGB, a source inside the prison where the Putin critic was being held has reportedly claimed.

Bruising found on the opposition leader's body was consistent with the 'one-punch' execution method, according to Russian exile and human rights campaigner Vladimir Osechkin.

'It is an old method of the KGB's special forces divisions,' he told The Times. 'They trained their operatives to kill a man with one punch in the heart, in the centre of the body. It was a hallmark of the KGB.'

Osechkin, founder of the Gulagu.net group which gathers testimony from prisoners and workers in Russia's notorious jails, says his information came from a source working in the arctic penal colony where Navalny died on Friday.

His widow has accused Putin of murdering her husband, claiming he was poisoned with the nerve agent Novichok and that Russian authorities are trying to cover up the assassination by refusing to release his body.

Osechkin, however, is not convinced and says that authorities would have been able to kill Navalny in any way they desired, and would not have wanted to 'leave a trace in his body and would lead directly back to Putin'.

He claims that Navalny had been forced to spend between two and a half to four hours in an open-air solitary confinement space where temperatures could dip to minus 27C the day before his death.

Prisoners are normally kept outdoors for no more than an hour and in far less extreme conditions.

'I think that they first destroyed his body by keeping him out in the cold for a long time and slowing the blood circulation down to a minimum,' Osechkin explained.

'And then it becomes very easy to kill someone, within seconds, if the operative has some experience in this.'

The single punch, a stealth assassination technique reputedly used by KGB special forces to avoid leaving any indication of cause of death, is then said to have been used.

Before becoming Russian leader, Putin famously served for some 15 years in the KGB as a foreign intelligence officer, retiring in 1990 with the rank of lieutenant colonel.

Russian authorities have so far failed to give a convincing explanation for the death of Navalny, the Russian president's most prominent critic.

According to the national penitentiary service, the 47-year-old died after taking a walk and feeling unwell.

Navalny's family has been told that they cannot have access to his body for another two weeks.

Osechkin said that he believes the presence of FSB officers at the prison to be evidence that Mr Navalny was murdered by the Kremlin.

He added: 'From what I know from my sources, it was a special operation that had been prepared several days in advance.'

'It was a command from Moscow because without Moscow it would not have been possible to dismantle the cameras in the way that they did.'

The development came after the Twitter account of Alexei Navalny's widow was briefly suspended yesterday for allegedly 'violating [its] rules' amid rising concern over the platform's political impartiality.

Yulia Navalnaya's account on X, formerly known as Twitter, was quickly reinstated following a wave of online criticism.