Finnish daily Iltalehti reported on Monday that  Sweden and Finland have agreed to both submit membership applications to the US-led NATO alliance as early as mid-May.

The daily said Stockholm suggested that "the two countries indicate their willingness to join" together, and that Helsinki agreed to do so  "as long as the Swedish government has made its decision."

On the Swedish side, Expressen cited that government sources have confirmed the report. The two countries' prime ministers had said that Russia's war in Ukraine changed Europe's "whole security landscape", prompting them to apply for NATO membership.

Finland's prime minister, whose country shares a 1,300 km border with Russia, mentioned on April 13 that the Nordic nation would decide whether to apply for NATO membership "within weeks", and that Sweden is also discussing joining the alliance.

Russia's foreign ministry said the choice was up to Finland and Sweden.

"But they should understand the consequences of such a step for our bilateral relations and for the architecture of European security as a whole," Spokesperson Maria Zakharova pointed out in a statement.