Sweden’s foreign ministry said on Tuesday it was expelling five Russian diplomats for conducting activities incompatible with their diplomatic status, saying the government took the security threat posed by Russian intelligence gathering very seriously.

Russia’s embassy in Sweden declined to comment on the development.

Russia and western countries have engaged in tit-for-tat expulsions since Moscow invaded Ukraine in February last year. Russia calls the invasion a “special military operation”.

“Five people who are employed at the (Russian) embassy have been asked to leave (Sweden) as a result of activities that are incompatible with the Vienna Convention on diplomatic relations,” a Swedish foreign ministry statement said.

The ministry declined to specify the activities involved but said the Swedish security service had reported that Russia had continuously engaged in intelligence gathering in Sweden. “This is a security threat that the government takes very seriously,” it said in an emailed statement.