MOSCOW — Russia said Thursday that it would expel four British diplomats and suspend counterterrorism cooperation with London in the latest step of a confrontation linked to the radiation poisoning death of a former KGB agent turned Kremlin critic.
Britain had announced Monday that it was expelling four Russian diplomats over Moscow's refusal to extradite Andrei Lugovoy, a Russian businessman accused of using polonium-210 to poison Alexander Litvinenko last year in London. The British government also said it would place restrictions on visas issued to Russian officials.
Moscow's response to the British action was "targeted, balanced and the minimum necessary," Foreign Ministry spokesman Mikhail Kamynin said.
Kamynin described London's actions as "provocative and unfriendly," and said that on visa issues Russia would mirror Britain's steps. Moscow has asked London to explain what visa restrictions it will be implementing, Kamynin said.
"Until clarification is given on the new practices, Russian officials will not be asking for British visas, and analogous visa requests by British officials will not be considered by us," he said.
It was not clear whether the mutual expulsions and other actions by the two sides had set the stage for further escalation of the confrontation or a gradual winding down of tensions over the killing of Litvinenko.
Russian President Vladimir V. Putin predicted Thursday that the conflict would ease.
"It is in our interest, both in the interest of Russia and in that of the U.K., that these relations should keep developing," Putin said in comments reported by the Russian news agency Interfax. "I'm sure that we will cope with this mini-crisis."
The Litvinenko case has particularly serious diplomatic implications because of the use of polonium-210 and because in a written statement prepared shortly before his death, Litvinenko accused Putin of ordering him killed.
The Kremlin has dismissed the charge as "nonsense."
Most of the world's polonium-210 is manufactured in Russia, and it is not a substance easily acquired in the quantity used to kill Litvinenko.
There has been considerable speculation that Moscow could retaliate further against London by taking steps against British economic interests in Russia. British Petroleum and Royal Dutch Shell, which is incorporated in Britain, are potential targets.
Putin and other top Russian officials have repeatedly pointed out that their nation's constitution bans extradition of Russian citizens to other countries, a point that British officials appeared to ignore for weeks.
But on Monday, British Foreign Secretary David Miliband acknowledged the issue and suggested in Parliament that Russia could amend its constitution to make it possible to extradite Lugovoy.
Kamynin ridiculed that suggestion Thursday.
"How can one demand that a sovereign democratic country change its constitution for the sake of handing over one suspect in the Litvinenko case?" he said.
Article 61 of the constitution states that "a citizen of the Russian Federation may not be deported out of Russia or extradited to another state."
Some observers have argued that Moscow could find a constitutional loophole enabling it to extradite Lugovoy, citing a sentence in Article 15 of the constitution that says "if an international treaty of the Russian Federation stipulates other rules than those stipulated by the law, the rules of the international treaty apply." However, the same article states that "laws and other legal acts adopted by the Russian Federation may not contravene the constitution."
Genrikh Padva, a prominent Moscow lawyer, said that although Article 15 has provided critics of Russia's stance with "a certain opportunity for discussion on this issue," it is clear that the constitution does in fact ban extradition of citizens.
"If the country where a Russian citizen committed a crime has enough evidence for a solid case, then it is possible that this person may be tried in Russia on these charges, but certainly not abroad," Padva said. "It is out of the question."
Britain has rejected the option of providing its evidence to Moscow and having Lugovoy put on trial in Russia.
Andrei Kortunov, president of the New Eurasia Foundation, a Moscow think tank, said it was unclear how much effect there would be from suspension of counter-terrorism cooperation and mutual restrictions on visas.
The visa spat could mean anything "from basically nothing to severing diplomatic relations," he said.
Kortunov noted the possibility of Russian retaliation against British economic interests, and suggested that Britain had more to lose than Russia if the dispute spilled over into this sphere.
"British energy companies such as British Petroleum and Shell have extensive interests in Russia and certainly don't want their positions damaged because of the Litvinenko case," he said. "That is why I think British options both in the legal and the political spheres are rather limited."
Times staff writer Sergei L. Loiko contributed to this report.