A London court has rejected a Russian request for the extradition of Chechen envoy Akhmed Zakayev.
Zakayev (centre) would have faced charges of kidnap and murder in Russia
The court accepted a plea by lawyers for Mr Zakayev that he would not get a fair trial - and could even could face torture - in Russia.
"It would be unjust and oppressive to return Mr Zakayev to Russia," Judge Timothy Workman ruled on Thursday.
Moscow responded by accusing the court of double standards and trying to politicise a criminal case.
Mr Zakayev has been accused of a range of crimes including kidnap, taking part in the murder of Russian soldiers and levying war.
The allegations relate to incidents between October 1995 and December 2000, when Chechnya was fighting for independence.
Mr Zakayev's defenders - who include the actress Vanessa Redgrave - had said the charges were politically motivated and that he would face torture if he was sent to Russia.
The judge at the hearing, Mr Workman of Bow Street Magistrates Court in central London, agreed, quoting evidence of torture given by witnesses.
"I have come to the inevitable conclusion that if the
[Russian] authorities are prepared to resort to torturing
witnesses, there is a substantial risk that Mr Zakayev
would himself be subject to torture," he said.
Amnesty International welcomed the statement.
"The widespread use of torture and ill-treatment by the
Russian authorities had given rise to well-based fears for
Akhmed Zakayev's physical safety if sent back to Russia," the human rights organisation said.
But the Russian Prosecutor-General's Office said the court had attempted to find a political overtone in what was a purely criminal case.
"Once again, terrorists are being split into two groups - good
terrorists and bad ones," the office said in a statement.
This is the third time in recent months that Britain has turned down a Russian request for the extradition of one of its citizens.
The wealthy businessman, Boris Berezovsky, and his business associate Yuly Dubov recently had their extradition cases thrown out, and both were granted political asylum.
BBC Russian affairs analyst Stephen Dalziel says it is not clear whether these cases will have a negative effect on the generally positive relations between London and Moscow.
Mr Zakayev has acted as a representative of Aslan Maskhadov, the rebel leader who considers himself president of Chechnya.
A pro-Moscow candidate, Akhmed Kadyrov, was elected Chechen president in an October vote that was condemned by observers and rejected by the rebels.