FACTBOX-Strains in British-Russian relations

(Reuters) - Russia said on Thursday it would expel four British diplomats, retaliating for Britain's decision to send home four Russian diplomats because Moscow refused to extradite murder suspect Andrei Lugovoy, a former Russian agent.

Following is a list of other major irritants:

* BORIS BEREZOVSKY:

-- Moscow resents London's granting refugee status to an outspoken Kremlin critic, Russian tycoon Boris Berezovsky. Britain has repeatedly rejected Russian requests to extradite Berezovsky, wanted in Moscow on several criminal charges. Berezovsky, who has lived in London since 2000, says the charges have been invented to silence him. Berezovsky said on Wednesday British police warned him in June of a plot to kill him, and he fled abroad, escaping a threat he said bore the hallmarks of Russia's security service.

* AKHMED ZAKAYEV:

-- Russia blames Britain for granting asylum to several leading Chechen rebels, most notably to Akhmed Zakayev. Russia says London's refusal to hand Zakayev over for trial betrays its double standards in dealing with terrorist threats.

* OIL AND GAS:

-- British oil firm BP was forced last month to sell its stake in the Siberian Kovykta gas field to state-controlled firm Gazprom at a knock-down price.

-- The deal became part of the Kremlin drive to tighten its grip over Russia's oil and gas resources, fuelling concerns in the West about the safety of energy supplies.