Two teenagers in Norway could face prosecution after causing damage to a 5,000-year-old rock carving, despite claiming they were trying to improve it.

The historical carving of a figure on skis is one of Norway’s most famous historical sites and provides some of the earliest evidence of skiing in the world.

The two boys, who remain anonymous, issued a public apology on Friday, and said they had been trying to repair the relic by carving over its outline to make the image clearer.

But Norwegian residents described the alteration as a “tragedy” for the nation’s cultural heritage, the Local reported.

“It’s a tragedy, because it’s one of the most famous Norwegian historical sites,” said Bård Anders Langø, the mayor of the nearby Alstahaug Municipality. “It is one of the most internationally known symbols of Norway.”

The original stone-age carving, before it was defaced by the two boys (NORDLAND FYLKESKOMMUNE)

Historians said they believed the damage done to the carving, located on the island of Tro off Nordland, northern Norway, is irreversible.

Tor-Kristian Storvik, an archaeologist for Nordland County who surveyed the carving on Sunday said the damage could be punishable under Norway’s Cultural Heritage Act.

As well as the skiing figure, a carving of a whale which formed part of the same hunting scene had also suffered serious damage from the vandalism.

Speaking to local media, Mr Storvik said he was pleased the vandals had come forward, but he was not prepared to retract the crime report sent to police.

“It’s a kid, and it was done out of good intentions,” he said. “They were trying to make it more visible actually, and I don’t think they understood how serious it was. I think now they understand.”