London The plot to poison Alexander Litvinenko, a former KGB colonel and outspoken critic of the Kremlin, seemed to have a cast of characters from a John Le Carre novel. It captured the imagination of the international media and raised unsettling questions about the alleged involvement of the Russian government and its ruthlessness in dealing with political enemies.
On Tuesday, the convoluted tale took another twist as Britain's Crown Prosecution Service made a formal request for the extradition of Andrei Lugovoi, another former KGB agent who had tea in a London hotel with Litvinenko on Nov. 1, the day Litvinenko fell ill.
But Russia's response to the extradition request was blunt: "In accordance with Russian law, citizens of Russia cannot be turned over to foreign states," said Marina Gridneva, a spokeswoman for the Russian prosecutor general's office.
Tuesday's extradition request, in which British officials said they had sufficient evidence to charge Lugovoi with "deliberate poisoning" in the "extraordinarily grave crime," had been expected for weeks.
A deepening chill between Russia and the West was apparent last week in an icy summit between Russian President Vladimir Putin and European Union leaders. The two sides traded barbs over energy policy and human rights. Russia also is angered by the Bush administration's efforts to place missile defense installations in eastern Europe.
Although the Russian Constitution prohibits the extradition of Russian citizens, the law does allow for the prosecution of a Russian citizen within Russia if there is evidence that the person committed a crime on foreign soil.
Gridneva, the spokeswoman for the prosecutor's office, said that Russian investigators would be willing to look at the evidence amassed by British prosecutors against Lugovoi but that they have yet to receive such material from British authorities.
Lugovoi worked at the KGB and its successor agency, the Federal Security Service, from 1987 to 1996.