More than 120 people have been injured, five of them critically, when a high-speed ferry coming from the Asian gambling hub of Macau smashed into an object in the water.

Firefighters said the hydrofoil carrying 163 passengers and 11 crew hit the unidentified object off a small island in Hong Kong's western waters on Sunday night. The ferry lost power after the collision, but it was not in any danger of sinking, rescuers said.

Ferry operator Shun Tak Holdings said a preliminary inspection found damage to the boat's rear wing and the engine room.

The hospital authority said a total of 124 people were hurt.

TV news channels showed passengers, some with bandages on their heads, arriving at a pier and being taken to waiting ambulances.

It is the fourth accident in two years on the hour-long ferry route between the coastal Chinese territories of Macau and Hong Kong.

Vessels depart around every 15 minutes on the route, which operates around the clock, taking passengers from the Asian financial centre of Hong Kong to Macau, a former Portuguese colony now known mainly for its glitzy casinos.

In a similar accident in November 2013, 87 people were hurt when a Macau hydrofoil hit a floating object off an outlying Hong Kong island. Last year a ferry hit a breakwater in Macau's harbour and another collided with a mainland Chinese cargo ship in separate incidents that left dozens injured.

Hong Kong suffered its biggest maritime tragedy in 2012 when a boat and commuter ferry collided, killing 39 people and injuring about 100.