Russian media reported earlier Thursday that Kovtun, a business partner of witness Andrei Lugovoi, had fallen into a coma after being questioned by Russian and British investigators probing Litvinenko's death.
Andrei Romashov, a lawyer for Lugovoi, a businessman and former Federal Protection Service officer, said: "I have just clarified the facts. This can only be called a provocation. Kovtun's condition is satisfactory."
The lawyer said he had spoken to representatives of Kovtun, also a witness in the Litvinenko murder case.
"I called them, and they said Kovtun feels normal," he said.
Russia's top prosecutors launched Thursday a criminal investigation into the poisoning of Russian security service defector Alexander Litvinenko, and into a related murder attempt on Kovtun.
The Prosecutor General's Office said the criminal cases were launched as a result of inspections which revealed that Litvinenko died after being poisoned with polonium-210, a radioactive isotope.
Dmitry Kovtun, who met with Litvinenko in London in October, was diagnosed with an illness also caused by radiation poisoning, the statement said.
Litvinenko, an outspoken critic of President Vladimir Putin's administration and a close associate of exiled oligarch Boris Berezovsky, died in a London hospital November 23, and was buried earlier Thursday in Highgate Cemetery.
