A new sign posted at Norway's river border with Russia reminds tourists feeling nature's call that it's against the law to pee in the direction of Russia -- on pain of a hefty fine.

Written in English in black block letters, the sign posted on the banks of the Jakobselva river that separates Norway from Russia reads: "No Peeing Towards Russia".

It is placed next to an official signpost informing people that the area is under video surveillance by Norwegian border guards.

"The sign was probably posted by well-intentioned people to warn passers-by against offensive behaviour," Norway's border commissioner Jens-Arne Hoilund told AFP, confirming a report on the internet site Barents Observer, which posted a picture of the new sign.

Infringers face a fine of 3,000 kroner (290 euros, $340).

The area is popular with tourists on the Norwegian side, where you can easily see Russia just a few metres (yards) away across the river.

"Urinating in nature is not necessarily offensive but it depends on your point of view. In this case it falls under the law banning offensive behaviour at the border," Hoilund said.

A Norwegian law prohibits "offensive behaviour at the border intended for the neighbouring state or its authorities."

According to Hoilund, who is tasked with ensuring that agreements regulating neighbourly relations between Norway and Russia are respected, Russian authorities have never complained about urination incidents at the border.

Barents Observer meanwhile recalled that four people were arrested by Norwegian border guards several years ago after throwing stones at the Russian side, and last winter, a woman filmed by a surveillance camera was fined 8,000 kroner for putting her left hand on the other side of the border.

"You may think that's severe, but we just apply the border rules as they are," Hoilund said.

Norway's 197.7-kilometre (123-mile) land border with Russia is NATO's northern border in the Arctic.

Oslo and Moscow have traditionally enjoyed good relations, though tensions have risen since Russia's 2014 invasion of the Crimean peninsula.