A British judge said Thursday that the Russian state has a case to answer in the radioactive poisoning of Alexander Litvinenko as he formally opened a public inquiry into the death of the former spy.

Judge Robert Owen said he would be able to hear secret evidence behind closed doors about the 2006 murder of Litvinenko, who accused President Vladimir Putin from his deathbed of being linked to his killing.

The British government finally agreed last week to open a full public inquiry into the death of Kremlin critic Litvinenko, in a move that threatens to increase tensions with Moscow amid the crisis in Ukraine.

Litvinenko, 43, an ex-agent in Russia's FSB intelligence agency who turned against his former masters, was poisoned with radioactive polonium-210 while drinking tea at a London hotel.

"The HM (Her Majesty's) government material taken alone, and in so far as it was relevant, established a prima facie case as to the culpability of the Russian state in Mr Litvinenko's death," Owen said as he opened the inquiry.

"The most important feature of the inquiry... is that it will permit me to consider closed evidence and hold closed hearings."

Secret evidence would not have been admissable under an inquest.

He said there would be a procedural hearing on September 5, but the hearing of evidence would not begin until January.

The inquiry is expected to last until the end of 2015.


'No link to MH17'

The judge began on Thursday by formally suspending an earlier inquest -- an inquest is a hearing under English law which examines how someone dies but does not apportion blame -- and opening the public inquiry.

The British government's decision to launch the inquiry was a major turnaround, as it had previously resisted all attempts to do so on the grounds of protecting sensitive information about Russian and British intelligence.

British Home Secretary Theresa May had originally wanted to wait for the results of the inquest. But three High Court judges ruled in February that May must reconsider that decision, following a challenge by Litvinenko's widow Marina.

Russia's ambassador to London, Alexander Yakovenko, last week said that Moscow would not accept the judgement of the inquiry if any of the evidence was given in secret.

Britain has strenuously denied any link between its decision to launch the probe and the ratcheting up of international pressure on Russia over the downing of Malaysia Airlines flight MH17 over Ukraine.

The Litvinenko murder outraged London at the time and plunged relations with Moscow into the deep freeze.

In a deathbed letter, Litvinenko said he believed Russia's president was involved in his killing after he publicly criticised the leader, himself an ex-Soviet KGB agent.

British police have identified Russian spy-turned-lawmaker Andrei Lugovoi as the chief suspect and have issued an arrest warrant for his fellow former agent Dmitri Kovtun, but Moscow has refused to hand them over.

They both deny involvement, while Lugovoi called the inquiry politically motivated.