MOSCOW — More than 50 British diplomats and technical support staff will be expelled from Russia, the Russian Foreign Ministry said Saturday, claiming that the move will establish parity with Russia’s diplomatic mission in Britain.

“Russia offered parity,” spokeswoman Maria Zakharova said. “The Brits have just over 50 more people.”

The move clarified Russia’s response to Britain’s expulsion in mid-March of 23 Russian diplomats and ratchets up an already tense situation between Russia and the West over the March 4 poisoning of a former Russian double agent on British soil.

The former spy and his daughter were poisoned allegedly by a Soviet-designed nerve agent, Novichok, a weapon believed to be unique to Russia. Russia has flatly denied the allegations and offered a variety of counterclaims.

Russia had previously expelled 23 British diplomats before Saturday’s announcement.

The latest expulsions were not unexpected. On Friday, Russia said it would limit the size of the British diplomatic mission to Russia to match that of Moscow’s mission in Britain. However, no figures were given, as Britain does not publish rosters of its embassies and consulates for security reasons.

Britain is not alone in facing the Kremlin’s retaliatory measures: 23 nations that supported Britain by expelling Russian diplomats were issued expulsion orders Friday. Russia described those actions as mirror responses.

In total, 59 diplomats from Germany, France and a number of other European nations are to be expelled.

In the past week, 27 nations joined Britain in expelling Russian diplomats. NATO and Georgia have also followed suit. At least 150 Russian diplomatic workers across the world have been handed expulsion orders.

The United States led the expulsion count with 60 Russian diplomats and added to its measures the closing of Russian Consulate in Seattle. Russia responded, expelling 60 U.S. diplomats and ordering the U.S. Consulate in St. Petersburg closed.

Tensions between Russia and Britain continue to escalate beyond the diplomatic realm. Friday night, the Russian Embassy in London said that an Aeroflot flight from London to Moscow was stopped for a search by British authorities. Russia has threatened to conduct similar searches of British Airways flights.

Meanwhile, the British Foreign Office has said it is considering granting Russia’s repeated requests for access to Yulia Skripal, daughter of former spy Sergei Skripal. Both were reported in critical condition after the March 4 attack.

British authorities said Thursday evening that Yulia’s condition was rapidly improving. Her father was described as still being in critical though stable condition.