HONG KONG (AFP) - An annual swim across Hong Kong's harbour has become the latest international sports event to be called off because of the unprecedented political unrest gripping the city, organisers announced on Friday (Oct 11).

This year's New World Harbour Race - where swimmers brave one of the world's most famous and busiest waterways - had been scheduled for Oct 27.

Organisers said they decided to scrap the event "after giving due consideration to the recent social situation and the resulting uncertainties".

Hong Kong has been shaken by four months of massive democracy protests which have seen increasingly violent clashes between hardcore demonstrators and police, as well as regular transport disruptions.

A string of high-profile sports and entertainment events have been cancelled as a result, including pop concerts, stand-up comedy shows and award-winning musicals.

On Wednesday, organisers pulled the plug on the city's premier squash event in December, the Hong Kong Squash Open, due to uncertainty caused by the protests.

The crisis has already forced the cancellation of the WTA Hong Kong Open tennis tournament and the postponement of a football friendly at home against Malaysia.

Organisers of the mixed martial arts event HK4 also announced on Wednesday a postponement to March next year, citing safety concerns.

The wave of protests in the international finance hub was sparked by opposition to a now-scrapped proposal to allow extraditions to mainland China, but have since morphed into a larger movement for democracy and police accountability.

The city enjoys unique rights under the terms of its handover to China by Britain in 1997, including freedom of expression and an independent judiciary, but many believe these are under threat from an increasingly assertive Beijing.

Street battles between riot police and small groups of protesters have become a weekly occurrence, hammering the already struggling economy, spooking tourists and undermining Hong Kong's reputation for stability.