Dmitry Kovtun, a contact of dead Russian ex-spy Alexander Litvinenko, is in critical condition in hospital from radiation poisoning, Interfax news agency quoted an unnamed source as saying on Thursday. "Doctors have classified Kovtun's condition as critical," Interfax quoted its source as saying. Kovtun met Litvinenko in London on November 1, the day the former spy fell ill.Interfax also reported that Kovtun fell into a coma after British and Russian investigators working on the Litvinenko case had finished questioning him in a Moscow hospital. However, it gave no source for the information on a coma. A spokesman for Russia's Prosecutor-General's office said he had no information about Kovtun's health. Russian prosecutors earlier opened a criminal investigation for the attempted murder of Kovtun, a businessman. They said Kovtun was displaying symptoms of radiation poisoning.