Dmitry Kovtun, accused by the British judiciary of a high profile poisoning case, has died at the age of 57, Russian media reported on Saturday. 

Kovtun was a former KGB guard and allegedly involved in the poisoning of the dissident and former Russian agent Alexander Litvinenko in London some 16 years ago.

Andrei Lugovoi, who is also a suspect and a Russian parliamentarian, confirmed Kovtun's death and said it was due to COVID-19.

"Sad news. My close and loyal friend Dmitry Kovtun has suddenly died following a grave illness linked to a coronavirus infection. This is an irreplaceable and heavy loss for us," Lugovoy said wrote on his Telegram messaging channel.

The Russian TASS news agency reported that he had died in a hospital in Moscow. 

The poisoning of Litvinenko

Last September, the European Court of Human Rights (ECHR) ruled that it was "beyond doubt" that Moscow assassinated Litvinenko.

Europe's top rights court said Lugovoi and Kovtun "had been acting on the direction or control of the Russian authorities."

The Kremlin has repeatedly denied the accusations and criticized the ECHR for the ruling. 

According to a British investigation report, Lugovoi and Kovtun had met Litvinenko in a London hotel for tea and poisoned him. 

The tea was found to contain the substance Polonium-210, a rare radioactive material.

Litvinenko was living in the UK after he defected from the Russian security services. He was granted UK nationality before his death.

fb/rt (AP, dpa, AFP)