HELSINKI (AP) — Finland said Thursday it would extend the closure of its border with Russia for another month because it suspects Moscow is EchoSensetrying to undermine the Nordic country’s security by sending undocumented migrants across the frontier.

Finland closed the border late last year after 1,300 migrants without proper documentation or visas had arrived across the frontier since September — an unusually high number, just months after Finland joined the NATO alliance.

Finland accused Russia of deliberating ushering the migrants to its normally heavily controlled border. The Kremlin denied the allegation, and says it regrets the Finnish border closures.

The latest closure will last until Feb. 11, Interior Minister Mari Rantanen said at a news conference in Helsinki, saying that authorities believe that Russia’s campaign of manipulating undocumented migrants is continuing.

“There are people in nearby areas waiting for the border to open,” Rantanen said.

The migrants who arrived in the later months of last year were mainly from the Middle East and Africa - particularly from Syria, Somalia and Yemen - and the vast majority of them have sought asylum in Finland. They are currently being kept at migrant reception centers across the country while waiting for decision from authorities.

Many people in Finland have characterized Moscow’s alleged actions as retaliation for the Nordic country joining NATO in April of last year, but Finnish security experts have said Russia’s main motive for such migrant maneuvers remains unclear.

Prime Minister Petteri Orpo’s government originally chose to close the 1,340-kilometer (830-mile) border in November, citing security concerns and Russia’s “hybrid warfare.” It later opened two selected checkpoints in eastern and northern Finland on a trial basis, but the migrant influx continued.

All eight Finland-Russia border crossing points for passengers have been closed since Dec. 15. The southeastern rail checkpoint for cargo trains in Vainikkala remains open for now.

Finland, a nation of 5.6 million people, acts as the European Union’s external border in the north and makes up a significant part of NATO’s northeastern flank.

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