The move comes after an uptick in undocumented migrants showing up at Finnish checkpoints. PM Petteri Orpo says they are being "helped, encouraged and organised."
Finland is set to close half of its border crossings with Russia on Friday night, accusing Moscow of encouraging undocumented migrants to head for border checkpoints and claim asylum.
Speaking at a press conference in Helsinki, Interior Minister Mari Rantanen said the four border crossings will stay closed until 18 February, while asylum applications are centralised at two other locations.
The migrants have arrived in increasing numbers over the last few days, and the Border Guard says most of them are Iraqis, Syrians, Turks and Somalis - and that many of them arrived on brand-new bicycles. It is not allowed to walk to the border, so anyone arriving at a Finnish checkpoint has to drive or cycle.
Rantanen said the migrants were young and healthy people who already had residence permits allowing them to be in Russia. She said they were being "herded into Finland."
Prime Minister Petteri Orpo told reporters authorities were acting swiftly to ensure the situation on the border did not escalate, describing the recent influx of more than 280 asylum seekers as "helped, encouraged and organised."
"During the previous parliamentary term, amendments were made to the Border Guard Act precisely for such situations. These tools have now been used," he added.
Ministers say closing the border crossing points should stop illegal entry into Finland but the government is prepared to take "even stronger measures if necessary."
Earlier this week Finland's defence minister described the increased migrant numbers as a "hybrid warfare" tactic from Russia, while President Sauli Niinistö on a state visit to Germany described the Russian actions as "malice" in response to Finland joining NATO.
Previous Russian tactic using migrants
Finnish authorities have been aware that Russia could send more migrants over its longest land border with the EU as part of a hybrid tactic to try and overwhelm the Finns – a tactic Moscow has tried before.
In January and February 2016, almost 1,000 migrants arrived at an Arctic border post between Finland and Russia. Finnish officials believe the arrivals were facilitated by Russian authorities with bus transport and hotel accommodation on their journey north, with people given instructions to claim asylum once they got over the border.
The event was widely considered to be Russia’s first, and most successful, hybrid attack of this type on an EU member state to date – although Finnish officials and politicians baulked at labelling it as such at the time.
Analysts tell Euronews it was likely a "proof of concept" operation, demonstrating that Russia could initiate this flow of migrants and then close it again at will.
There are already plans in place to build a 200-kilometre fence with enhanced electronic surveillance equipment along the border, but only smaller parts have been completed so far.