"Obviously, the decision to join Finland and Sweden in NATO does not strengthen the security of the region, but, on the contrary, complicates the situation with ensuring security for all," TASS quoted Medvedev as saying.
He also noted that Russia would be able to ensure its security if Sweden and Finland join the North Atlantic Alliance.
Earlier, Turkish President Recep Tayyip Erdogan allowed Ankara to freeze the process of Sweden and Finland joining NATO if they do not fulfill a number of Turkish conditions.
The US Senate Foreign Affairs Committee has approved the protocols for Finland and Sweden to join NATO.
Russian President Vladimir Putin noted that the country will be forced to respond mirror to the possible deployment of NATO military infrastructure in Finland and Sweden after the countries join the alliance.