A tiny mistake ended a Finnish karaoke club marathon that set a new world record Monday for the longest sing-along session of more than 18 days.

The Kouvola Karaoke Club began singing on July 2, and the Guinness Book of World Records awarded the club a world record certificate on July 11 after they beat the previous record of 214 hours held by a club in China.

The group had vowed to carry on the marathon for another couple of weeks, aiming to sing for 600 hours non-stop.

But the effort faltered after precisely 446 hours, four minutes and five seconds when the the same song was performed twice within two hours, which is against the rules.

"At first it felt bad that the marathon was ended by human error. But the figures are great, the record is more than twice as long as the old one," Arto Nikunen, the president of the club, told AFP.

On Wednesday a party celebrating the world record will be held in Kouvola, a small town some 135 kilometres (85 miles) northeast of Helsinki.