"You know the general practice, countermeasures usually reflect the actions of the other side," Petrov said at a press conference on Monday. He added that a corresponding reaction from Russia should be expected also this time, pointing out that Russia recently reacted to the UK's expelling 23 Russian diplomats by simply expelling 23 British diplomats.

Foreign Minister Sven Mikser (SDE) told the media on Monday that Estonia is expelling the Russian military attaché from the country in response to the Salisbury chemical attack. "As the activities of this employee of the Russian Embassy are not compatible with the diplomatic status as agreed on in the Vienna Convention, we have decided to expel the diplomat. We informed the ambassador of the Russian Federation of the diplomat's expulsion from Estonia today," Mikser said.

According to Petrov, Estonia's decision was not a surprise. Asked who of the Estonian diplomats in Russia will be expelled in turn, Petrov said that it is too early to talk about that.

"These decisions are not made that quickly. I informed Moscow of my conversation at the Estonian Ministry of Foreign Affairs as well as of the decision made in regard to the Russian military attaché," Petrov said on Monday evening. Petrov was summoned to the ministry at 3 p.m. yesterday.

"Time is needed to make a deliberate decision. Any kind of emotion will only be harmful here. Although there is also a military attaché working in Moscow, like in our embassy," he added.

Estonia's military attaché in Moscow is Col. Toomas Peda.