MOSCOW — Russia's chief prosecutor said Tuesday that a potential suspect in the London poisoning death of dissident former KGB agent Alexander Litvinenko had been hospitalized and that British investigators would be allowed to see him only if doctors approved.
Prosecutor General Yuri Chaika also said that Russia's constitution forbade the extradition of citizens and that if any Russians were identified as suspects in the case they would not be sent to Britain and could be tried only in Russia.
Despite earlier top-level pledges of Russian cooperation in the case, Chaika indicated that British investigators might face formidable obstacles pursuing leads in Russia.
Former KGB agent Andrei Lugovoy, who met with Litvinenko in London on the day he was thought to have been radioactively poisoned, had expressed willingness to speak to investigators. But on Tuesday a man answering Lugovoy's cellphone said that it was not clear "whether and when he will be able to talk" to investigators or how long he would remain in the hospital.
The man, who identified himself as an aide named Alexander, said he was not authorized to comment on the nature of Lugovoy's hospitalization. Chaika said he thought Lugovoy was "undergoing medical treatment" but said nothing about his illness.
In a statement written shortly before his death on Nov. 23, Litvinenko blamed Russian President Vladimir V. Putin for his poisoning, a charge the Kremlin angrily dismissed. Litvinenko also told friends that he thought Lugovoy might have been the person who poisoned him.
Chaika, speaking at a news conference, said the questioning of witnesses and potential suspects would be carried out by Russians in the presence of British investigators, who arrived in Moscow on Monday. It was unclear whether British investigators would be allowed to ask questions.
"They will not interrogate anyone," Chaika said at one point. Later he indicated that British investigators might be allowed to ask some questions, with permission, on a case-by-case basis.
"We interrogate and they are present. They interrogate in our presence," he said. "We should perform those investigative actions and they can take part in this with our permission. We may even deny them the right to take part. But we will do this together with them. We want them to take part."
The prosecutor's office has not launched an investigation of its own and will only assist British investigators, Chaika said.
