The Kremlin stated on Monday that Finland and Sweden's decision to join NATO will not strengthen European security.

Kremlin Spokesperson Dmitry Peskov told reporters that "we are not convinced that Finland and Sweden joining NATO will somehow strengthen or improve the security architecture on our continent," adding that "this is a serious issue, an issue that raises our concern, and we will follow very carefully what will be the consequences of this accession of Finland and Sweden to NATO in a practical sense in terms of our security, which must be ensured in an absolutely unconditional manner."

He did, however, highlight that, unlike Ukraine, Russia has no territorial problems with Finland or Sweden.

Deputy Foreign Minister Sergei Ryabkov said earlier on Monday that the decision was a "grave mistake with far-reaching consequences."

Finland and Sweden are prepared to abandon decades of military non-alignment in order to join NATO as a "defense" against expected Russian "aggression".

Read more: Italian leader criticizes Finland, Sweden plans to join NATO

Moscow has warned Finland that it would take reciprocal steps, and the Finnish President spoke with Russian President Vladimir Putin on Saturday about the ordeal.

Kremlin calls US special services behavior towards Russian missions staff unacceptable 

Additionally, the Kremlin Spokesperson slammed the behavior of the US special services with the employees of Russia's foreign missions as arrogant and unacceptable.

When asked whether Moscow is aware of threats to Russian embassy employees mentioned by Antonov, Peskov told reporters, "There is such information in the Kremlin. We really share the concerns of the head of our diplomatic mission in the United States [Anatoly Antonov]. The behavior of a representative of the US special services in relation to our citizens, employees of our foreign missions is very impudent. We consider it unacceptable."