The European Court of Human Rights (ECHR) announced Monday that Russia has been deemed responsible for the death of Alexander Litvinenko, a former Russian agent turned Kremlin critic who died in London by polonium poisoning in 2006.

CNN reports that the ruling found "Russia was responsible for assassination of Aleksandr Litvinenko in the UK."

"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," it said, referring to the names of two Russian agents accused of killing Litvinenko.

According to the Court, Russian authorities "had not carried out an effective domestic investigation capable of leading to the establishment of the facts and, where appropriate, the identification and punishment of those responsible for the murder."