Andrei Lugovoi, a key witness in the probe into the death of former Russian spy Alexander Litvinenko, was questioned on Monday by Russian and British detectives, Itar-Tass news agency reported.

Scotland Yard detectives and Russian prosecutors visited a Moscow hospital that specializes in treating radiation cases on Monday and interrogated Andrei Lugovoi on the afternoon, the Russian news agency said.

Lugovoi told Itar-Tass that the questioning lasted three hours. "I gave testimony exclusively as a witness. I was officially informed of that before the interrogation," Itar-Tass quoted him as saying after questioning.

The British investigators arrived in Moscow on Dec. 4. They and their Russian colleagues interviewed Russian businessman Dmitry Kovtun, another key figure in the case, last week.

German investigators have been focusing on Kovtun since traces of polonium-210, the radioactive element that killed Litvinenko, were found in and around Hamburg last week.

Kovtun visited the city, where his ex-wife lives, on the eve of his Nov. 1 trip to London, where he and Lugovoi met with Litvinenko. Litvinenko said he fell ill that day and he died three weeks later.

Kovtun has also been diagnosed with radiation sickness.

Editor: Yan