Russia on Thursday expelled 60 American diplomats and closed the United States consulate in St Petersburg in retaliation to similar action by the United States over the nerve agent attack on a former Russian spy in the United Kingdom. On March 26, the US had expelled 60 Russian diplomats and closed a consulate in Seattle.

Russia has repeatedly denied any role in the nerve agent attack on former double agent Sergei Skripal and his daughter Yulia in southern England’s Salisbury on March 4. The father and daughter are still reportedly in hospital.

Russia’s Foreign Ministry asked 58 US diplomats in Moscow and two in Yekaterinburg to leave the country by April 5 after declaring them “persona non grata” for what it called activities incompatible with diplomatic status. Russia’s Foreign Minister Sergei Lavrov said other countries that expelled its diplomats could expect a symmetrical response, BBC reported.

Lavrov said Moscow was reacting to the “absolutely unacceptable action” taken against the country under pressure from the United States and Britain. He accused the United Kingdom of “forcing everyone to follow an anti-Russian course” and said Britain was making a mockery of international law, The Guardian reported.

The White House said Russia’s decision only worsened the relationship between Washington and Moscow. “Russia’s response was not unanticipated and the United States will deal with it,” the White House said in a statement.

Nearly two dozen countries have expelled at least 140 Russian diplomats in the last few days, including over 100 on Monday alone. This is believed to be the largest collective expulsion of Russian diplomats in history.