Finland has closed four of its border crossings with Russia to try to halt a surge in asylum seekers it says was instigated by Moscow,
BBC reports.
Helsinki accused its neighbour of channelling migrants to the crossings in retaliation for it joining Nato.
Kremlin spokesman Dmitry Peskov said Finland was making a "big mistake" and destroying bilateral relations.
Around 300 asylum seekers have arrived in Finland this week, according to border guards.
The Finnish Border Guard said barriers would be put up from midnight on Friday at the Vaalimaa, Nuijamaa, Imatra and Niirala border posts in south-east Finland.
These points have seen a surge in illegal crossings by citizens of countries including Syria, Yemen and Iraq.
Mr Peskov said: "(One can) only express deep regret that the Finnish authorities have taken the path of destroying bilateral relations," Russian state news agency TASS reported.
"Russia has never in modern history threatened Finland, we had no reason for any confrontation. Now they have chosen this path.
"From our point of view, this is a big mistake."
Finland's prime minister Petteri Orpo accused Russia of deliberately helping people without the proper documents to get to the border.
