Finland's prime minister said on Wednesday that the country will close all but its northernmost border crossing with Russia, following a surge in migrants which Finland claims Russia is intentionally pushing to the border.

Since the beginning of August, around 700 asylum seekers have entered Finland without a visa over its eastern border.

"The government has today decided to close more border posts. Only Raja-Jooseppi station will remain open," Prime Minister Petteri Orpo told a press conference.

After seeing a surge in migrants seeking asylum on its eastern border in November, Finland last week shut half of its eight crossings to Russia.

"Unfortunately, these measures have not been able to stop this phenomenon," Orpo said.

The government said that "it is clear that foreign authorities and other actors have played a role in facilitating the entry of persons crossing the border into Finland."

"The situation also involves international crime," the government said in a statement.

Earlier in October, the Finnish border guard sounded the alarm about a change in Russia's policy, as it began allowing migrants without proper documentation to cross the border.

"This is a systematic and organised action by the Russian authorities," Orpo said on Monday.

Border crossings will be closed starting on Friday and will initially remain closed until December 23.

Russian Foreign Ministry spokeswoman Maria Zakharova has rejected allegations that Russia is deliberately pushing migrants to the Finnish border.

"Finnish authorities are beginning to make clumsy excuses, warming up Russophobic sentiments," she said in a statement.

Finland's relationship with its eastern neighbour soured following the start of Russia's war in Ukraine – prompting Finland to accede to the Nato alliance in April. (AFP)