Britain’s government said Wednesday it has expelled a Russian diplomat and a diplomatic spouse in a tit-for-tat response to the expulsion of two British embassy staff in Moscow earlier this week.

In a statement Wednesday, the Foreign Office said it had summoned the Russian ambassador to the U.K., Andrei Kelin, following an “increasingly aggressive and coordinated campaign of harassment against British diplomats.”

It said Kelin was told that the U.K. will “not stand for intimidation of British embassy staff and their families.” As a result, the Foreign Office was taking “immediate reciprocal action, revoking accreditation for a Russian diplomat and a diplomatic spouse.”