"After what we had to deal with, and are still dealing with on the Polish-Belarus border, and considering the opening of the skies above the Kaliningrad region for aeroplanes from Turkey, Syria and Belarus, it could be in the coming weeks," Sobolewski later told Reuters, referring to increasing arrivals of migrants.
Kremlin spokesman Dmitry Peskov told reporters in a briefing that Russia would not interfere with any such decision.
"History proves the stupidity of decisions to build walls every time, because over the years or decades, all walls fall," he said.