The U.K. expelled a top Russian envoy and imposed new restrictions on the country¡¯s diplomats, in one of the most high-profile responses yet to what allied officials describe as a coordinated espionage campaign to weaken support for Ukraine.

Home Secretary James Cleverly announced the actions in Parliament on Wednesday, saying the U.K. would deport Russia¡¯s defense attache on the grounds that he was an undeclared spy. He said would also limit the amount of time the country¡¯s diplomats can spend in the U.K., as well as strip some Russian-owned properties ¡ª including its defense section in London¡¯s Highgate area and a 19th century country house south of the capital ¡ª of diplomatic protection.

The actions come in response to a suspected arson attack against Ukrainian-linked properties in East London and other espionage activities in Britain and Europe, Cleverly said.