MOSCOW, March 17 (Xinhua) -- The Russian Foreign Ministry expelled 23 British diplomats on Saturday in a retaliatory move over British punitive measures against Russia and the former Russian spy attack row.

"A total of 23 diplomatic employees of the British Embassy in Moscow are declared personae non gratae and must leave within a week," said the statement, warning that Moscow retained the right to respond if Britain continues to take unfriendly steps against Russia.

The ministry also revoked its approval of the opening and operation of the British Consulate General in the Russian city of St. Petersburg, saying that "the British Council's activities are being ceased due to its unregulated status in the Russian Federation."

Russia has notified London of the retaliatory measures in relation with the so-called 'Skripal case,' British Ambassador to Russia Laurie Bristow confirmed on Saturday after being summoned to the foreign ministry.

The response comes amid a deterioration of London-Moscow relations over the consequent British punitive measures against Russia and the former Russian spy attack row.

On Wednesday British Prime Minister Theresa May announced a series of measures against Russia over its failure to respond to the British government's request to explain how a military-grade nerve agent was used in a recent attack on former Russian spy Sergei Skripal and his daughter.

The measures included the expulsion of 23 diplomats in a week, the freezing of Russian state assets in Britain, the suspension of all planned high-level bilateral contacts and boycotting the ministers and the Royal Family from attending the FIFA World Cup in Russia.

Skripal, a former Russian intelligence officer, and his 33-year-old daughter Yulia were found unconscious on a bench at a shopping center in the district of Salisbury, Britain, on March 5, and are still in critical condition, according to reports.

The Russian government has denied any involvement in the attack.