This year some 42 Norwegian reindeer have crossed the boundary to graze in the Russian national park Pasvik Zapovednik.

Norwegian authorities said Thursday they would mend a fence near Norway's border with Russia in the far north to stop its reindeer from making costly crossings over the international boundary.

In a bid to prevent the four-footed intrusions, a fence already exists on the Norwegian side, spanning 150 kilometers (93 miles) of the countries' shared 198-kilometer border.

But some sections, dating as far back as 1954, have fallen into such disrepair that the animals can easily pass through and cross into Russia.

"It is strictly forbidden to cross the border into Russia, for reindeer too," the Norwegian Directorate of Agriculture said in a statement.

Since the beginning of the year, 42 Norwegian reindeer have crossed the boundary to graze in the Russian national park Pasvik Zapovednik.

Each time it happens, Russian authorities demand some 50,000 kroner ($4,700) in damages and the animals are slaughtered on their return to Norway to prevent a recurrence.

The Directorate of Agriculture has therefore ordered the construction of a new fence on a seven-kilometer section by October 1, at a cost of 3.7 million kroner.

The reindeer—bred by the indigenous Sami herders that span northern Europe—are semi-nomadic and travel across vast expanses as they move between their winter and summer grazing grounds.

In this Arctic region, Norway and Russia share just one authorized land crossing, the Storskog-Boris Gleb border point.