STRASBOURG -- Russia was responsible for the killing of Alexander Litvinenko, the European Court of Human Rights (ECHR) has found, according to a BBC report.

Litvinenko, a former Russian spy who became a British citizen, died of polonium poisoning in 2006 in London.

A UK public inquiry conducted in 2016 concluded that the killing was "probably approved" by Russian President Vladimir Putin.

Russia has always denied any involvement in his murder.

The UK inquiry said former KGB bodyguard Andrei Lugovoi and another Russian, Dmitry Kovtun deliberately poisoned Litvinenko by putting the radioactive substance into his drink.

Litvinenko's widow, Marina, took the case against Russia to the Strasbourg-based rights court, which has agreed with the UK inquiry's conclusion.

"The Court found in particular that there was a strong prima facie case that, in poisoning Mr Litvinenko, Mr Lugovoi and Mr Kovtun had been acting as agents of the Russian state," the ECHR ruled.

It concluded that Russia's failure to refute claims that it organised the hit further pointed towards the state's responsibility.

Both Lugovoi and Kovtun have denied any involvement in the killing.