The Finnish Border Guard on Friday announced it would erect barriers from midnight local time at the Vaalimaa, Nuijamaa, Imatra and Niirala border posts in southeast Finland, which account for much of the travel between the two countries.

“We have had bigger numbers like on Monday, 39 and on Wednesday, 75. Yesterday was quite peaceful, but today again over 100 irregular immigrants have come to the southeast district of Finland,” Captain Jussi Vainikka of the Finnish Border Guards told Reuters in Nuijamaa.

The Finnish government has accused Russia of funnelling migrants to the crossings in retaliation for its decision to increase defence cooperation with the US, an assertion dismissed by the Kremlin.

Finland shares a 1,340-kilometre border with Russia that also serves as the EU’s external border. Some 300 asylum seekers, mostly from Iraq, Yemen, Somalia and Syria, have arrived in Finland this week, according to the Border Guard.

A fifth border post had already been shut for passengers when train services between the two countries were suspended last year, while four regular border crossings remain open for the time being.

Asylum can now only be sought at two of those, in Salla and Vartius, the Border Guard said.

The Kremlin on Friday said Finland was making a “big mistake” by closing down border crossings and that Helsinki’s move was destroying bilateral relations.

European Union border agency Frontex on Friday told Reuters it would send officers to Finland to help safeguard the frontier.

Finland’s finance minister Riikka Purra of the anti-immigration Finns Party in a television interview on Thursday said her country was ready to close all crossing points on the Russian border if necessary.

Finland’s ombudsman for non-discrimination this week said Helsinki still had a duty under international treaties and EU law to allow asylum seekers to seek protection.