A collection of Bitcoin (virtual currency) tokens are displayed in this picture illustration taken December 8, 2017. REUTERS/Benoit Tessier/Illustration

LONDON (Reuters) - Bitcoin fell below $5,000 on Monday for the first time in over a year, slumping to a fresh 13-month low on the Bitstamp platform as a broad sell-off in cryptocurrencies sparked last week gathered momentum.

As of 1645 GMT the original cryptocurrency was down 8.7 percent at $5,100, after breaching the landmark for the first time since Oct. 12, 2017.

Traders said selling was largely sentiment-driven and cited fears that Thursday’s “hard fork” in bitcoin cash, where the smaller coin split into two separate currencies, could destabilise others.